ETH Price: $2,542.54 (-4.34%)

Transaction Decoder

Block:
13423696 at Oct-15-2021 04:24:37 PM +UTC
Transaction Fee:
0.013204186526696676 ETH $33.57
Gas Used:
81,746 Gas / 161.527004706 Gwei

Account State Difference:

  Address   Before After State Difference Code
0x679a4218...A99EF67Bd 1.265602302461560811 Eth1.664602302461560835 Eth0.399000000000000024
0x8A3fECD0...758942abf 8.846942402120988977 Eth9.777942402120989033 Eth0.931000000000000056
0x9b1e6D7c...baAF0E7e2 0.47937892115681113 Eth0.678878921156811142 Eth0.199500000000000012
0xAd7Ad048...5D91Fe398 2.660000000000000161 Eth0.000000000000000001 Eth2.66000000000000016
(Binance Pool)
8,856.923346531492557548 Eth8,856.923428277492557548 Eth0.000081746
0xd23F42e3...233C9750c 0 Eth0.399000000000000024 Eth0.399000000000000024
0xdA00A06A...b9f196880 0.394955638795159277 Eth1.126455638795159321 Eth0.731500000000000044
0xf3b6e73d...E6d75937e
(Rocket Riders: Deployer)
0.03448360295709893 Eth
Nonce: 24
0.021279416430402254 Eth
Nonce: 25
0.013204186526696676

Execution Trace

RocketRiders.CALL( )
  • ETH 0.931000000000000056 0x8a3fecd0348da48d5fe4dc05b2897d2758942abf.CALL( )
  • ETH 0.731500000000000044 0xda00a06ab3bbd3544b79c1350c463cab9f196880.CALL( )
  • ETH 0.399000000000000024 0xd23f42e3dc8769f38de085a52b81e76233c9750c.CALL( )
  • ETH 0.399000000000000024 0x679a4218aaca587bbf1c863780d6149a99ef67bd.CALL( )
  • ETH 0.199500000000000012 0x9b1e6d7c3d29d83877907b212ee4bf9baaf0e7e2.CALL( )
    // SPDX-License-Identifier: MIT
    pragma solidity ^0.8.0;
    import "@openzeppelin/contracts/token/ERC721/extensions/ERC721Enumerable.sol";
    import "@openzeppelin/contracts/access/Ownable.sol";
    contract RocketRiders is Ownable, ERC721Enumerable {
        using Strings for uint256;
        string public baseURI;
        uint256 public cost = 0.07 ether;
        uint256 public constant maxSupply = 9950;
        uint256 public maxMintAmount = 10;
        bool public paused = true;
        uint256 internal once = 5;
        uint256 public constant maxTraits = 6;
        uint16[][maxTraits] internal tp;
        uint16[maxTraits][maxSupply] internal rocketRiderGenome;
        address internal a1;
        address internal a2;
        address internal a3;
        address internal a4;
        address internal a5;
        constructor(
            string memory _name,
            string memory _symbol,
            string memory _initBaseURI,
            address _a1,
            address _a2,
            address _a3,
            address _a4,
            address _a5
        ) ERC721(_name, _symbol) {
            setBaseURI(_initBaseURI);
            a1 = _a1;
            a2 = _a2;
            a3 = _a3;
            a4 = _a4;
            a5 = _a5;
            tp[0] = [
                1,
                1,
                1,
                1,
                1,
                1,
                1,
                1,
                2,
                2,
                2,
                2,
                2,
                2,
                2,
                2,
                2,
                2,
                3,
                3,
                3,
                3,
                3,
                3,
                3,
                3,
                3,
                4,
                4,
                4,
                4,
                4,
                4,
                4,
                4,
                4,
                4,
                5,
                5,
                5,
                5,
                5,
                5,
                5,
                5,
                5,
                5,
                5,
                5,
                5,
                5,
                5,
                6,
                6,
                6,
                6,
                6,
                6,
                7,
                7,
                7,
                7,
                7,
                7,
                7,
                7,
                7,
                7,
                7,
                7,
                7,
                7,
                7,
                7,
                7,
                8,
                8,
                8,
                8,
                8,
                8,
                8,
                8,
                8,
                8,
                9,
                9,
                9,
                9,
                9,
                9,
                9,
                9,
                9,
                10,
                10,
                10,
                10,
                10,
                11
            ];
            tp[1] = [
                1,
                1,
                1,
                1,
                1,
                1,
                1,
                1,
                1,
                1,
                1,
                1,
                2,
                2,
                2,
                2,
                2,
                2,
                2,
                2,
                2,
                2,
                2,
                2,
                2,
                2,
                2,
                3,
                3,
                3,
                3,
                3,
                4,
                4,
                4,
                4,
                4,
                4,
                4,
                4,
                4,
                4,
                4,
                4,
                4,
                4,
                4,
                5,
                5,
                5,
                5,
                5,
                5,
                5,
                5,
                5,
                5,
                5,
                5,
                5,
                5,
                5,
                5,
                5,
                5,
                5,
                5,
                6,
                7,
                7,
                7,
                7,
                7,
                7,
                7,
                7,
                7,
                7,
                8,
                8,
                8,
                8,
                8,
                8,
                8,
                8,
                8,
                8,
                8,
                8,
                8,
                8,
                8,
                8,
                8,
                8,
                8,
                8,
                9,
                9
            ];
            tp[2] = [
                1,
                2,
                2,
                2,
                2,
                2,
                2,
                2,
                2,
                2,
                2,
                3,
                3,
                3,
                3,
                3,
                3,
                3,
                3,
                3,
                3,
                4,
                4,
                4,
                4,
                4,
                4,
                5,
                5,
                5,
                5,
                5,
                5,
                5,
                6,
                6,
                6,
                6,
                6,
                7,
                7,
                7,
                7,
                7,
                7,
                7,
                8,
                8,
                8,
                8,
                9,
                9,
                10,
                11,
                12,
                12,
                12,
                12,
                12,
                12,
                13,
                13,
                13,
                13,
                13,
                14,
                15,
                16,
                16,
                16,
                16,
                16,
                16,
                16,
                16,
                16,
                16,
                16,
                17,
                18,
                19,
                20,
                20,
                21,
                21,
                22,
                22,
                22,
                22,
                22,
                22,
                22,
                22,
                22,
                22,
                22,
                22,
                23,
                23,
                24
            ];
            tp[3] = [
                1,
                2,
                2,
                3,
                4,
                5,
                5,
                5,
                5,
                5,
                5,
                5,
                5,
                6,
                6,
                6,
                6,
                6,
                6,
                6,
                7,
                7,
                7,
                8,
                8,
                9,
                9,
                9,
                9,
                9,
                10,
                10,
                10,
                10,
                10,
                10,
                11,
                12,
                12,
                12,
                12,
                12,
                12,
                12,
                13,
                13,
                13,
                14,
                14,
                14,
                14,
                14,
                14,
                14,
                14,
                15,
                15,
                15,
                15,
                15,
                16,
                16,
                16,
                16,
                16,
                17,
                17,
                17,
                17,
                18,
                19,
                19,
                19,
                19,
                19,
                19,
                20,
                20,
                20,
                20,
                20,
                21,
                21,
                21,
                22,
                23,
                23,
                23,
                23,
                23,
                23,
                23,
                24,
                24,
                25,
                26,
                27,
                28,
                28,
                29
            ];
            tp[4] = [
                1,
                1,
                1,
                2,
                2,
                2,
                2,
                3,
                4,
                5,
                5,
                5,
                5,
                5,
                5,
                5,
                5,
                5,
                6,
                6,
                6,
                6,
                6,
                6,
                6,
                7,
                7,
                7,
                7,
                7,
                7,
                7,
                7,
                8,
                8,
                8,
                8,
                8,
                8,
                8,
                8,
                9,
                9,
                9,
                9,
                9,
                9,
                9,
                10,
                10,
                10,
                11,
                12,
                13,
                13,
                13,
                13,
                13,
                13,
                13,
                13,
                13,
                14,
                14,
                14,
                14,
                14,
                14,
                14,
                14,
                15,
                15,
                15,
                15,
                15,
                15,
                15,
                16,
                17,
                17,
                17,
                17,
                17,
                17,
                17,
                17,
                17,
                18,
                18,
                18,
                18,
                18,
                18,
                18,
                18,
                19,
                20,
                21,
                22,
                23
            ];
            tp[5] = [
                1,
                1,
                1,
                1,
                1,
                2,
                2,
                2,
                2,
                2,
                3,
                3,
                3,
                4,
                4,
                4,
                5,
                5,
                6,
                6,
                7,
                7,
                7,
                7,
                7,
                7,
                8,
                8,
                9,
                9,
                9,
                9,
                9,
                9,
                9,
                10,
                10,
                10,
                10,
                10,
                11,
                11,
                11,
                11,
                12,
                12,
                12,
                13,
                13,
                14,
                14,
                15,
                15,
                15,
                15,
                15,
                16,
                16,
                16,
                16,
                16,
                17,
                17,
                17,
                17,
                17,
                18,
                19,
                19,
                20,
                21,
                21,
                21,
                21,
                21,
                22,
                22,
                22,
                22,
                22,
                23,
                23,
                23,
                23,
                23,
                23,
                23,
                23,
                23,
                23,
                23,
                23,
                23,
                23,
                23,
                23,
                23,
                23,
                23,
                23
            ];
        }
        function mint(address _to, uint256 _mintAmount) public payable {
            uint256 supply = totalSupply();
            if (msg.sender != owner()) {
                require(supply + _mintAmount <= maxSupply);
                require(!paused);
                require(_mintAmount > 0 && _mintAmount <= maxMintAmount);
                require(msg.value >= cost * _mintAmount);
            }
            uint256 randomNumber = uint256(
                keccak256(
                    abi.encodePacked(once, block.difficulty, block.timestamp, _to)
                )
            );
            for (uint256 i = 1; i <= _mintAmount; i++) {
                configureRider(randomNumber, supply + i);
                _safeMint(_to, supply + i);
            }
        }
        function configureRider(uint256 randomNumber, uint256 id) internal {
            for (uint8 i = 0; i < maxTraits; i++) {
                once++;
                rocketRiderGenome[id][i] = createDNA(i, randomNumber);
            }
        }
        function createDNA(uint8 traitType, uint256 randomNumber)
            internal
            view
            returns (uint16)
        {
            uint16 i = uint16(
                uint256(keccak256(abi.encodePacked(once, randomNumber++))) %
                    tp[traitType].length
            );
            uint16 result = tp[traitType][i];
            return result;
        }
        function getRiderDNA(uint256 tokenId)
            public
            view
            returns (
                uint256,
                uint256,
                uint256,
                uint256,
                uint256,
                uint256
            )
        {
            require(
                _exists(tokenId),
                "ERC721Metadata: DNA query for nonexistent token"
            );
            return (
                rocketRiderGenome[tokenId][0],
                rocketRiderGenome[tokenId][1],
                rocketRiderGenome[tokenId][2],
                rocketRiderGenome[tokenId][3],
                rocketRiderGenome[tokenId][4],
                rocketRiderGenome[tokenId][5]
            );
        }
        function _baseURI() internal view virtual override returns (string memory) {
            return baseURI;
        }
        function setBaseURI(string memory _newBaseURI) public onlyOwner {
            baseURI = _newBaseURI;
        }
        function tokenURI(uint256 tokenId)
            public
            view
            virtual
            override
            returns (string memory)
        {
            require(
                _exists(tokenId),
                "ERC721Metadata: URI query for nonexistent token"
            );
            return
                bytes(_baseURI()).length > 0
                    ? string(abi.encodePacked(_baseURI(), tokenId.toString()))
                    : "";
        }
        function setMaxMintAmount(uint256 _maxMintAmount) public onlyOwner {
            maxMintAmount = _maxMintAmount;
        }
        function setCost(uint256 _newCost) public onlyOwner {
            cost = _newCost;
        }
        function pause(bool _state) public onlyOwner {
            paused = _state;
        }
        function withdraw() public payable onlyOwner {
            uint256 amount = address(this).balance;
            require(payable(a1).send((amount * 350) / 1000));
            require(payable(a2).send((amount * 275) / 1000));
            require(payable(a3).send((amount * 150) / 1000));
            require(payable(a4).send((amount * 150) / 1000));
            require(payable(a5).send((amount * 75) / 1000));
        }
        function getBalance() public view returns (uint256) {
            return address(this).balance;
        }
    }
    // SPDX-License-Identifier: MIT
    pragma solidity ^0.8.0;
    /**
     * @dev Interface of the ERC165 standard, as defined in the
     * https://eips.ethereum.org/EIPS/eip-165[EIP].
     *
     * Implementers can declare support of contract interfaces, which can then be
     * queried by others ({ERC165Checker}).
     *
     * For an implementation, see {ERC165}.
     */
    interface IERC165 {
        /**
         * @dev Returns true if this contract implements the interface defined by
         * `interfaceId`. See the corresponding
         * https://eips.ethereum.org/EIPS/eip-165#how-interfaces-are-identified[EIP section]
         * to learn more about how these ids are created.
         *
         * This function call must use less than 30 000 gas.
         */
        function supportsInterface(bytes4 interfaceId) external view returns (bool);
    }
    // SPDX-License-Identifier: MIT
    pragma solidity ^0.8.0;
    import "./IERC165.sol";
    /**
     * @dev Implementation of the {IERC165} interface.
     *
     * Contracts that want to implement ERC165 should inherit from this contract and override {supportsInterface} to check
     * for the additional interface id that will be supported. For example:
     *
     * ```solidity
     * function supportsInterface(bytes4 interfaceId) public view virtual override returns (bool) {
     *     return interfaceId == type(MyInterface).interfaceId || super.supportsInterface(interfaceId);
     * }
     * ```
     *
     * Alternatively, {ERC165Storage} provides an easier to use but more expensive implementation.
     */
    abstract contract ERC165 is IERC165 {
        /**
         * @dev See {IERC165-supportsInterface}.
         */
        function supportsInterface(bytes4 interfaceId) public view virtual override returns (bool) {
            return interfaceId == type(IERC165).interfaceId;
        }
    }
    // SPDX-License-Identifier: MIT
    pragma solidity ^0.8.0;
    /**
     * @dev String operations.
     */
    library Strings {
        bytes16 private constant _HEX_SYMBOLS = "0123456789abcdef";
        /**
         * @dev Converts a `uint256` to its ASCII `string` decimal representation.
         */
        function toString(uint256 value) internal pure returns (string memory) {
            // Inspired by OraclizeAPI's implementation - MIT licence
            // https://github.com/oraclize/ethereum-api/blob/b42146b063c7d6ee1358846c198246239e9360e8/oraclizeAPI_0.4.25.sol
            if (value == 0) {
                return "0";
            }
            uint256 temp = value;
            uint256 digits;
            while (temp != 0) {
                digits++;
                temp /= 10;
            }
            bytes memory buffer = new bytes(digits);
            while (value != 0) {
                digits -= 1;
                buffer[digits] = bytes1(uint8(48 + uint256(value % 10)));
                value /= 10;
            }
            return string(buffer);
        }
        /**
         * @dev Converts a `uint256` to its ASCII `string` hexadecimal representation.
         */
        function toHexString(uint256 value) internal pure returns (string memory) {
            if (value == 0) {
                return "0x00";
            }
            uint256 temp = value;
            uint256 length = 0;
            while (temp != 0) {
                length++;
                temp >>= 8;
            }
            return toHexString(value, length);
        }
        /**
         * @dev Converts a `uint256` to its ASCII `string` hexadecimal representation with fixed length.
         */
        function toHexString(uint256 value, uint256 length) internal pure returns (string memory) {
            bytes memory buffer = new bytes(2 * length + 2);
            buffer[0] = "0";
            buffer[1] = "x";
            for (uint256 i = 2 * length + 1; i > 1; --i) {
                buffer[i] = _HEX_SYMBOLS[value & 0xf];
                value >>= 4;
            }
            require(value == 0, "Strings: hex length insufficient");
            return string(buffer);
        }
    }
    // SPDX-License-Identifier: MIT
    pragma solidity ^0.8.0;
    /**
     * @dev Provides information about the current execution context, including the
     * sender of the transaction and its data. While these are generally available
     * via msg.sender and msg.data, they should not be accessed in such a direct
     * manner, since when dealing with meta-transactions the account sending and
     * paying for execution may not be the actual sender (as far as an application
     * is concerned).
     *
     * This contract is only required for intermediate, library-like contracts.
     */
    abstract contract Context {
        function _msgSender() internal view virtual returns (address) {
            return msg.sender;
        }
        function _msgData() internal view virtual returns (bytes calldata) {
            return msg.data;
        }
    }
    // SPDX-License-Identifier: MIT
    pragma solidity ^0.8.0;
    /**
     * @dev Collection of functions related to the address type
     */
    library Address {
        /**
         * @dev Returns true if `account` is a contract.
         *
         * [IMPORTANT]
         * ====
         * It is unsafe to assume that an address for which this function returns
         * false is an externally-owned account (EOA) and not a contract.
         *
         * Among others, `isContract` will return false for the following
         * types of addresses:
         *
         *  - an externally-owned account
         *  - a contract in construction
         *  - an address where a contract will be created
         *  - an address where a contract lived, but was destroyed
         * ====
         */
        function isContract(address account) internal view returns (bool) {
            // This method relies on extcodesize, which returns 0 for contracts in
            // construction, since the code is only stored at the end of the
            // constructor execution.
            uint256 size;
            assembly {
                size := extcodesize(account)
            }
            return size > 0;
        }
        /**
         * @dev Replacement for Solidity's `transfer`: sends `amount` wei to
         * `recipient`, forwarding all available gas and reverting on errors.
         *
         * https://eips.ethereum.org/EIPS/eip-1884[EIP1884] increases the gas cost
         * of certain opcodes, possibly making contracts go over the 2300 gas limit
         * imposed by `transfer`, making them unable to receive funds via
         * `transfer`. {sendValue} removes this limitation.
         *
         * https://diligence.consensys.net/posts/2019/09/stop-using-soliditys-transfer-now/[Learn more].
         *
         * IMPORTANT: because control is transferred to `recipient`, care must be
         * taken to not create reentrancy vulnerabilities. Consider using
         * {ReentrancyGuard} or the
         * https://solidity.readthedocs.io/en/v0.5.11/security-considerations.html#use-the-checks-effects-interactions-pattern[checks-effects-interactions pattern].
         */
        function sendValue(address payable recipient, uint256 amount) internal {
            require(address(this).balance >= amount, "Address: insufficient balance");
            (bool success, ) = recipient.call{value: amount}("");
            require(success, "Address: unable to send value, recipient may have reverted");
        }
        /**
         * @dev Performs a Solidity function call using a low level `call`. A
         * plain `call` is an unsafe replacement for a function call: use this
         * function instead.
         *
         * If `target` reverts with a revert reason, it is bubbled up by this
         * function (like regular Solidity function calls).
         *
         * Returns the raw returned data. To convert to the expected return value,
         * use https://solidity.readthedocs.io/en/latest/units-and-global-variables.html?highlight=abi.decode#abi-encoding-and-decoding-functions[`abi.decode`].
         *
         * Requirements:
         *
         * - `target` must be a contract.
         * - calling `target` with `data` must not revert.
         *
         * _Available since v3.1._
         */
        function functionCall(address target, bytes memory data) internal returns (bytes memory) {
            return functionCall(target, data, "Address: low-level call failed");
        }
        /**
         * @dev Same as {xref-Address-functionCall-address-bytes-}[`functionCall`], but with
         * `errorMessage` as a fallback revert reason when `target` reverts.
         *
         * _Available since v3.1._
         */
        function functionCall(
            address target,
            bytes memory data,
            string memory errorMessage
        ) internal returns (bytes memory) {
            return functionCallWithValue(target, data, 0, errorMessage);
        }
        /**
         * @dev Same as {xref-Address-functionCall-address-bytes-}[`functionCall`],
         * but also transferring `value` wei to `target`.
         *
         * Requirements:
         *
         * - the calling contract must have an ETH balance of at least `value`.
         * - the called Solidity function must be `payable`.
         *
         * _Available since v3.1._
         */
        function functionCallWithValue(
            address target,
            bytes memory data,
            uint256 value
        ) internal returns (bytes memory) {
            return functionCallWithValue(target, data, value, "Address: low-level call with value failed");
        }
        /**
         * @dev Same as {xref-Address-functionCallWithValue-address-bytes-uint256-}[`functionCallWithValue`], but
         * with `errorMessage` as a fallback revert reason when `target` reverts.
         *
         * _Available since v3.1._
         */
        function functionCallWithValue(
            address target,
            bytes memory data,
            uint256 value,
            string memory errorMessage
        ) internal returns (bytes memory) {
            require(address(this).balance >= value, "Address: insufficient balance for call");
            require(isContract(target), "Address: call to non-contract");
            (bool success, bytes memory returndata) = target.call{value: value}(data);
            return verifyCallResult(success, returndata, errorMessage);
        }
        /**
         * @dev Same as {xref-Address-functionCall-address-bytes-}[`functionCall`],
         * but performing a static call.
         *
         * _Available since v3.3._
         */
        function functionStaticCall(address target, bytes memory data) internal view returns (bytes memory) {
            return functionStaticCall(target, data, "Address: low-level static call failed");
        }
        /**
         * @dev Same as {xref-Address-functionCall-address-bytes-string-}[`functionCall`],
         * but performing a static call.
         *
         * _Available since v3.3._
         */
        function functionStaticCall(
            address target,
            bytes memory data,
            string memory errorMessage
        ) internal view returns (bytes memory) {
            require(isContract(target), "Address: static call to non-contract");
            (bool success, bytes memory returndata) = target.staticcall(data);
            return verifyCallResult(success, returndata, errorMessage);
        }
        /**
         * @dev Same as {xref-Address-functionCall-address-bytes-}[`functionCall`],
         * but performing a delegate call.
         *
         * _Available since v3.4._
         */
        function functionDelegateCall(address target, bytes memory data) internal returns (bytes memory) {
            return functionDelegateCall(target, data, "Address: low-level delegate call failed");
        }
        /**
         * @dev Same as {xref-Address-functionCall-address-bytes-string-}[`functionCall`],
         * but performing a delegate call.
         *
         * _Available since v3.4._
         */
        function functionDelegateCall(
            address target,
            bytes memory data,
            string memory errorMessage
        ) internal returns (bytes memory) {
            require(isContract(target), "Address: delegate call to non-contract");
            (bool success, bytes memory returndata) = target.delegatecall(data);
            return verifyCallResult(success, returndata, errorMessage);
        }
        /**
         * @dev Tool to verifies that a low level call was successful, and revert if it wasn't, either by bubbling the
         * revert reason using the provided one.
         *
         * _Available since v4.3._
         */
        function verifyCallResult(
            bool success,
            bytes memory returndata,
            string memory errorMessage
        ) internal pure returns (bytes memory) {
            if (success) {
                return returndata;
            } else {
                // Look for revert reason and bubble it up if present
                if (returndata.length > 0) {
                    // The easiest way to bubble the revert reason is using memory via assembly
                    assembly {
                        let returndata_size := mload(returndata)
                        revert(add(32, returndata), returndata_size)
                    }
                } else {
                    revert(errorMessage);
                }
            }
        }
    }
    // SPDX-License-Identifier: MIT
    pragma solidity ^0.8.0;
    import "../IERC721.sol";
    /**
     * @title ERC-721 Non-Fungible Token Standard, optional metadata extension
     * @dev See https://eips.ethereum.org/EIPS/eip-721
     */
    interface IERC721Metadata is IERC721 {
        /**
         * @dev Returns the token collection name.
         */
        function name() external view returns (string memory);
        /**
         * @dev Returns the token collection symbol.
         */
        function symbol() external view returns (string memory);
        /**
         * @dev Returns the Uniform Resource Identifier (URI) for `tokenId` token.
         */
        function tokenURI(uint256 tokenId) external view returns (string memory);
    }
    // SPDX-License-Identifier: MIT
    pragma solidity ^0.8.0;
    import "../IERC721.sol";
    /**
     * @title ERC-721 Non-Fungible Token Standard, optional enumeration extension
     * @dev See https://eips.ethereum.org/EIPS/eip-721
     */
    interface IERC721Enumerable is IERC721 {
        /**
         * @dev Returns the total amount of tokens stored by the contract.
         */
        function totalSupply() external view returns (uint256);
        /**
         * @dev Returns a token ID owned by `owner` at a given `index` of its token list.
         * Use along with {balanceOf} to enumerate all of ``owner``'s tokens.
         */
        function tokenOfOwnerByIndex(address owner, uint256 index) external view returns (uint256 tokenId);
        /**
         * @dev Returns a token ID at a given `index` of all the tokens stored by the contract.
         * Use along with {totalSupply} to enumerate all tokens.
         */
        function tokenByIndex(uint256 index) external view returns (uint256);
    }
    // SPDX-License-Identifier: MIT
    pragma solidity ^0.8.0;
    import "../ERC721.sol";
    import "./IERC721Enumerable.sol";
    /**
     * @dev This implements an optional extension of {ERC721} defined in the EIP that adds
     * enumerability of all the token ids in the contract as well as all token ids owned by each
     * account.
     */
    abstract contract ERC721Enumerable is ERC721, IERC721Enumerable {
        // Mapping from owner to list of owned token IDs
        mapping(address => mapping(uint256 => uint256)) private _ownedTokens;
        // Mapping from token ID to index of the owner tokens list
        mapping(uint256 => uint256) private _ownedTokensIndex;
        // Array with all token ids, used for enumeration
        uint256[] private _allTokens;
        // Mapping from token id to position in the allTokens array
        mapping(uint256 => uint256) private _allTokensIndex;
        /**
         * @dev See {IERC165-supportsInterface}.
         */
        function supportsInterface(bytes4 interfaceId) public view virtual override(IERC165, ERC721) returns (bool) {
            return interfaceId == type(IERC721Enumerable).interfaceId || super.supportsInterface(interfaceId);
        }
        /**
         * @dev See {IERC721Enumerable-tokenOfOwnerByIndex}.
         */
        function tokenOfOwnerByIndex(address owner, uint256 index) public view virtual override returns (uint256) {
            require(index < ERC721.balanceOf(owner), "ERC721Enumerable: owner index out of bounds");
            return _ownedTokens[owner][index];
        }
        /**
         * @dev See {IERC721Enumerable-totalSupply}.
         */
        function totalSupply() public view virtual override returns (uint256) {
            return _allTokens.length;
        }
        /**
         * @dev See {IERC721Enumerable-tokenByIndex}.
         */
        function tokenByIndex(uint256 index) public view virtual override returns (uint256) {
            require(index < ERC721Enumerable.totalSupply(), "ERC721Enumerable: global index out of bounds");
            return _allTokens[index];
        }
        /**
         * @dev Hook that is called before any token transfer. This includes minting
         * and burning.
         *
         * Calling conditions:
         *
         * - When `from` and `to` are both non-zero, ``from``'s `tokenId` will be
         * transferred to `to`.
         * - When `from` is zero, `tokenId` will be minted for `to`.
         * - When `to` is zero, ``from``'s `tokenId` will be burned.
         * - `from` cannot be the zero address.
         * - `to` cannot be the zero address.
         *
         * To learn more about hooks, head to xref:ROOT:extending-contracts.adoc#using-hooks[Using Hooks].
         */
        function _beforeTokenTransfer(
            address from,
            address to,
            uint256 tokenId
        ) internal virtual override {
            super._beforeTokenTransfer(from, to, tokenId);
            if (from == address(0)) {
                _addTokenToAllTokensEnumeration(tokenId);
            } else if (from != to) {
                _removeTokenFromOwnerEnumeration(from, tokenId);
            }
            if (to == address(0)) {
                _removeTokenFromAllTokensEnumeration(tokenId);
            } else if (to != from) {
                _addTokenToOwnerEnumeration(to, tokenId);
            }
        }
        /**
         * @dev Private function to add a token to this extension's ownership-tracking data structures.
         * @param to address representing the new owner of the given token ID
         * @param tokenId uint256 ID of the token to be added to the tokens list of the given address
         */
        function _addTokenToOwnerEnumeration(address to, uint256 tokenId) private {
            uint256 length = ERC721.balanceOf(to);
            _ownedTokens[to][length] = tokenId;
            _ownedTokensIndex[tokenId] = length;
        }
        /**
         * @dev Private function to add a token to this extension's token tracking data structures.
         * @param tokenId uint256 ID of the token to be added to the tokens list
         */
        function _addTokenToAllTokensEnumeration(uint256 tokenId) private {
            _allTokensIndex[tokenId] = _allTokens.length;
            _allTokens.push(tokenId);
        }
        /**
         * @dev Private function to remove a token from this extension's ownership-tracking data structures. Note that
         * while the token is not assigned a new owner, the `_ownedTokensIndex` mapping is _not_ updated: this allows for
         * gas optimizations e.g. when performing a transfer operation (avoiding double writes).
         * This has O(1) time complexity, but alters the order of the _ownedTokens array.
         * @param from address representing the previous owner of the given token ID
         * @param tokenId uint256 ID of the token to be removed from the tokens list of the given address
         */
        function _removeTokenFromOwnerEnumeration(address from, uint256 tokenId) private {
            // To prevent a gap in from's tokens array, we store the last token in the index of the token to delete, and
            // then delete the last slot (swap and pop).
            uint256 lastTokenIndex = ERC721.balanceOf(from) - 1;
            uint256 tokenIndex = _ownedTokensIndex[tokenId];
            // When the token to delete is the last token, the swap operation is unnecessary
            if (tokenIndex != lastTokenIndex) {
                uint256 lastTokenId = _ownedTokens[from][lastTokenIndex];
                _ownedTokens[from][tokenIndex] = lastTokenId; // Move the last token to the slot of the to-delete token
                _ownedTokensIndex[lastTokenId] = tokenIndex; // Update the moved token's index
            }
            // This also deletes the contents at the last position of the array
            delete _ownedTokensIndex[tokenId];
            delete _ownedTokens[from][lastTokenIndex];
        }
        /**
         * @dev Private function to remove a token from this extension's token tracking data structures.
         * This has O(1) time complexity, but alters the order of the _allTokens array.
         * @param tokenId uint256 ID of the token to be removed from the tokens list
         */
        function _removeTokenFromAllTokensEnumeration(uint256 tokenId) private {
            // To prevent a gap in the tokens array, we store the last token in the index of the token to delete, and
            // then delete the last slot (swap and pop).
            uint256 lastTokenIndex = _allTokens.length - 1;
            uint256 tokenIndex = _allTokensIndex[tokenId];
            // When the token to delete is the last token, the swap operation is unnecessary. However, since this occurs so
            // rarely (when the last minted token is burnt) that we still do the swap here to avoid the gas cost of adding
            // an 'if' statement (like in _removeTokenFromOwnerEnumeration)
            uint256 lastTokenId = _allTokens[lastTokenIndex];
            _allTokens[tokenIndex] = lastTokenId; // Move the last token to the slot of the to-delete token
            _allTokensIndex[lastTokenId] = tokenIndex; // Update the moved token's index
            // This also deletes the contents at the last position of the array
            delete _allTokensIndex[tokenId];
            _allTokens.pop();
        }
    }
    // SPDX-License-Identifier: MIT
    pragma solidity ^0.8.0;
    /**
     * @title ERC721 token receiver interface
     * @dev Interface for any contract that wants to support safeTransfers
     * from ERC721 asset contracts.
     */
    interface IERC721Receiver {
        /**
         * @dev Whenever an {IERC721} `tokenId` token is transferred to this contract via {IERC721-safeTransferFrom}
         * by `operator` from `from`, this function is called.
         *
         * It must return its Solidity selector to confirm the token transfer.
         * If any other value is returned or the interface is not implemented by the recipient, the transfer will be reverted.
         *
         * The selector can be obtained in Solidity with `IERC721.onERC721Received.selector`.
         */
        function onERC721Received(
            address operator,
            address from,
            uint256 tokenId,
            bytes calldata data
        ) external returns (bytes4);
    }
    // SPDX-License-Identifier: MIT
    pragma solidity ^0.8.0;
    import "../../utils/introspection/IERC165.sol";
    /**
     * @dev Required interface of an ERC721 compliant contract.
     */
    interface IERC721 is IERC165 {
        /**
         * @dev Emitted when `tokenId` token is transferred from `from` to `to`.
         */
        event Transfer(address indexed from, address indexed to, uint256 indexed tokenId);
        /**
         * @dev Emitted when `owner` enables `approved` to manage the `tokenId` token.
         */
        event Approval(address indexed owner, address indexed approved, uint256 indexed tokenId);
        /**
         * @dev Emitted when `owner` enables or disables (`approved`) `operator` to manage all of its assets.
         */
        event ApprovalForAll(address indexed owner, address indexed operator, bool approved);
        /**
         * @dev Returns the number of tokens in ``owner``'s account.
         */
        function balanceOf(address owner) external view returns (uint256 balance);
        /**
         * @dev Returns the owner of the `tokenId` token.
         *
         * Requirements:
         *
         * - `tokenId` must exist.
         */
        function ownerOf(uint256 tokenId) external view returns (address owner);
        /**
         * @dev Safely transfers `tokenId` token from `from` to `to`, checking first that contract recipients
         * are aware of the ERC721 protocol to prevent tokens from being forever locked.
         *
         * Requirements:
         *
         * - `from` cannot be the zero address.
         * - `to` cannot be the zero address.
         * - `tokenId` token must exist and be owned by `from`.
         * - If the caller is not `from`, it must be have been allowed to move this token by either {approve} or {setApprovalForAll}.
         * - If `to` refers to a smart contract, it must implement {IERC721Receiver-onERC721Received}, which is called upon a safe transfer.
         *
         * Emits a {Transfer} event.
         */
        function safeTransferFrom(
            address from,
            address to,
            uint256 tokenId
        ) external;
        /**
         * @dev Transfers `tokenId` token from `from` to `to`.
         *
         * WARNING: Usage of this method is discouraged, use {safeTransferFrom} whenever possible.
         *
         * Requirements:
         *
         * - `from` cannot be the zero address.
         * - `to` cannot be the zero address.
         * - `tokenId` token must be owned by `from`.
         * - If the caller is not `from`, it must be approved to move this token by either {approve} or {setApprovalForAll}.
         *
         * Emits a {Transfer} event.
         */
        function transferFrom(
            address from,
            address to,
            uint256 tokenId
        ) external;
        /**
         * @dev Gives permission to `to` to transfer `tokenId` token to another account.
         * The approval is cleared when the token is transferred.
         *
         * Only a single account can be approved at a time, so approving the zero address clears previous approvals.
         *
         * Requirements:
         *
         * - The caller must own the token or be an approved operator.
         * - `tokenId` must exist.
         *
         * Emits an {Approval} event.
         */
        function approve(address to, uint256 tokenId) external;
        /**
         * @dev Returns the account approved for `tokenId` token.
         *
         * Requirements:
         *
         * - `tokenId` must exist.
         */
        function getApproved(uint256 tokenId) external view returns (address operator);
        /**
         * @dev Approve or remove `operator` as an operator for the caller.
         * Operators can call {transferFrom} or {safeTransferFrom} for any token owned by the caller.
         *
         * Requirements:
         *
         * - The `operator` cannot be the caller.
         *
         * Emits an {ApprovalForAll} event.
         */
        function setApprovalForAll(address operator, bool _approved) external;
        /**
         * @dev Returns if the `operator` is allowed to manage all of the assets of `owner`.
         *
         * See {setApprovalForAll}
         */
        function isApprovedForAll(address owner, address operator) external view returns (bool);
        /**
         * @dev Safely transfers `tokenId` token from `from` to `to`.
         *
         * Requirements:
         *
         * - `from` cannot be the zero address.
         * - `to` cannot be the zero address.
         * - `tokenId` token must exist and be owned by `from`.
         * - If the caller is not `from`, it must be approved to move this token by either {approve} or {setApprovalForAll}.
         * - If `to` refers to a smart contract, it must implement {IERC721Receiver-onERC721Received}, which is called upon a safe transfer.
         *
         * Emits a {Transfer} event.
         */
        function safeTransferFrom(
            address from,
            address to,
            uint256 tokenId,
            bytes calldata data
        ) external;
    }
    // SPDX-License-Identifier: MIT
    pragma solidity ^0.8.0;
    import "./IERC721.sol";
    import "./IERC721Receiver.sol";
    import "./extensions/IERC721Metadata.sol";
    import "../../utils/Address.sol";
    import "../../utils/Context.sol";
    import "../../utils/Strings.sol";
    import "../../utils/introspection/ERC165.sol";
    /**
     * @dev Implementation of https://eips.ethereum.org/EIPS/eip-721[ERC721] Non-Fungible Token Standard, including
     * the Metadata extension, but not including the Enumerable extension, which is available separately as
     * {ERC721Enumerable}.
     */
    contract ERC721 is Context, ERC165, IERC721, IERC721Metadata {
        using Address for address;
        using Strings for uint256;
        // Token name
        string private _name;
        // Token symbol
        string private _symbol;
        // Mapping from token ID to owner address
        mapping(uint256 => address) private _owners;
        // Mapping owner address to token count
        mapping(address => uint256) private _balances;
        // Mapping from token ID to approved address
        mapping(uint256 => address) private _tokenApprovals;
        // Mapping from owner to operator approvals
        mapping(address => mapping(address => bool)) private _operatorApprovals;
        /**
         * @dev Initializes the contract by setting a `name` and a `symbol` to the token collection.
         */
        constructor(string memory name_, string memory symbol_) {
            _name = name_;
            _symbol = symbol_;
        }
        /**
         * @dev See {IERC165-supportsInterface}.
         */
        function supportsInterface(bytes4 interfaceId) public view virtual override(ERC165, IERC165) returns (bool) {
            return
                interfaceId == type(IERC721).interfaceId ||
                interfaceId == type(IERC721Metadata).interfaceId ||
                super.supportsInterface(interfaceId);
        }
        /**
         * @dev See {IERC721-balanceOf}.
         */
        function balanceOf(address owner) public view virtual override returns (uint256) {
            require(owner != address(0), "ERC721: balance query for the zero address");
            return _balances[owner];
        }
        /**
         * @dev See {IERC721-ownerOf}.
         */
        function ownerOf(uint256 tokenId) public view virtual override returns (address) {
            address owner = _owners[tokenId];
            require(owner != address(0), "ERC721: owner query for nonexistent token");
            return owner;
        }
        /**
         * @dev See {IERC721Metadata-name}.
         */
        function name() public view virtual override returns (string memory) {
            return _name;
        }
        /**
         * @dev See {IERC721Metadata-symbol}.
         */
        function symbol() public view virtual override returns (string memory) {
            return _symbol;
        }
        /**
         * @dev See {IERC721Metadata-tokenURI}.
         */
        function tokenURI(uint256 tokenId) public view virtual override returns (string memory) {
            require(_exists(tokenId), "ERC721Metadata: URI query for nonexistent token");
            string memory baseURI = _baseURI();
            return bytes(baseURI).length > 0 ? string(abi.encodePacked(baseURI, tokenId.toString())) : "";
        }
        /**
         * @dev Base URI for computing {tokenURI}. If set, the resulting URI for each
         * token will be the concatenation of the `baseURI` and the `tokenId`. Empty
         * by default, can be overriden in child contracts.
         */
        function _baseURI() internal view virtual returns (string memory) {
            return "";
        }
        /**
         * @dev See {IERC721-approve}.
         */
        function approve(address to, uint256 tokenId) public virtual override {
            address owner = ERC721.ownerOf(tokenId);
            require(to != owner, "ERC721: approval to current owner");
            require(
                _msgSender() == owner || isApprovedForAll(owner, _msgSender()),
                "ERC721: approve caller is not owner nor approved for all"
            );
            _approve(to, tokenId);
        }
        /**
         * @dev See {IERC721-getApproved}.
         */
        function getApproved(uint256 tokenId) public view virtual override returns (address) {
            require(_exists(tokenId), "ERC721: approved query for nonexistent token");
            return _tokenApprovals[tokenId];
        }
        /**
         * @dev See {IERC721-setApprovalForAll}.
         */
        function setApprovalForAll(address operator, bool approved) public virtual override {
            require(operator != _msgSender(), "ERC721: approve to caller");
            _operatorApprovals[_msgSender()][operator] = approved;
            emit ApprovalForAll(_msgSender(), operator, approved);
        }
        /**
         * @dev See {IERC721-isApprovedForAll}.
         */
        function isApprovedForAll(address owner, address operator) public view virtual override returns (bool) {
            return _operatorApprovals[owner][operator];
        }
        /**
         * @dev See {IERC721-transferFrom}.
         */
        function transferFrom(
            address from,
            address to,
            uint256 tokenId
        ) public virtual override {
            //solhint-disable-next-line max-line-length
            require(_isApprovedOrOwner(_msgSender(), tokenId), "ERC721: transfer caller is not owner nor approved");
            _transfer(from, to, tokenId);
        }
        /**
         * @dev See {IERC721-safeTransferFrom}.
         */
        function safeTransferFrom(
            address from,
            address to,
            uint256 tokenId
        ) public virtual override {
            safeTransferFrom(from, to, tokenId, "");
        }
        /**
         * @dev See {IERC721-safeTransferFrom}.
         */
        function safeTransferFrom(
            address from,
            address to,
            uint256 tokenId,
            bytes memory _data
        ) public virtual override {
            require(_isApprovedOrOwner(_msgSender(), tokenId), "ERC721: transfer caller is not owner nor approved");
            _safeTransfer(from, to, tokenId, _data);
        }
        /**
         * @dev Safely transfers `tokenId` token from `from` to `to`, checking first that contract recipients
         * are aware of the ERC721 protocol to prevent tokens from being forever locked.
         *
         * `_data` is additional data, it has no specified format and it is sent in call to `to`.
         *
         * This internal function is equivalent to {safeTransferFrom}, and can be used to e.g.
         * implement alternative mechanisms to perform token transfer, such as signature-based.
         *
         * Requirements:
         *
         * - `from` cannot be the zero address.
         * - `to` cannot be the zero address.
         * - `tokenId` token must exist and be owned by `from`.
         * - If `to` refers to a smart contract, it must implement {IERC721Receiver-onERC721Received}, which is called upon a safe transfer.
         *
         * Emits a {Transfer} event.
         */
        function _safeTransfer(
            address from,
            address to,
            uint256 tokenId,
            bytes memory _data
        ) internal virtual {
            _transfer(from, to, tokenId);
            require(_checkOnERC721Received(from, to, tokenId, _data), "ERC721: transfer to non ERC721Receiver implementer");
        }
        /**
         * @dev Returns whether `tokenId` exists.
         *
         * Tokens can be managed by their owner or approved accounts via {approve} or {setApprovalForAll}.
         *
         * Tokens start existing when they are minted (`_mint`),
         * and stop existing when they are burned (`_burn`).
         */
        function _exists(uint256 tokenId) internal view virtual returns (bool) {
            return _owners[tokenId] != address(0);
        }
        /**
         * @dev Returns whether `spender` is allowed to manage `tokenId`.
         *
         * Requirements:
         *
         * - `tokenId` must exist.
         */
        function _isApprovedOrOwner(address spender, uint256 tokenId) internal view virtual returns (bool) {
            require(_exists(tokenId), "ERC721: operator query for nonexistent token");
            address owner = ERC721.ownerOf(tokenId);
            return (spender == owner || getApproved(tokenId) == spender || isApprovedForAll(owner, spender));
        }
        /**
         * @dev Safely mints `tokenId` and transfers it to `to`.
         *
         * Requirements:
         *
         * - `tokenId` must not exist.
         * - If `to` refers to a smart contract, it must implement {IERC721Receiver-onERC721Received}, which is called upon a safe transfer.
         *
         * Emits a {Transfer} event.
         */
        function _safeMint(address to, uint256 tokenId) internal virtual {
            _safeMint(to, tokenId, "");
        }
        /**
         * @dev Same as {xref-ERC721-_safeMint-address-uint256-}[`_safeMint`], with an additional `data` parameter which is
         * forwarded in {IERC721Receiver-onERC721Received} to contract recipients.
         */
        function _safeMint(
            address to,
            uint256 tokenId,
            bytes memory _data
        ) internal virtual {
            _mint(to, tokenId);
            require(
                _checkOnERC721Received(address(0), to, tokenId, _data),
                "ERC721: transfer to non ERC721Receiver implementer"
            );
        }
        /**
         * @dev Mints `tokenId` and transfers it to `to`.
         *
         * WARNING: Usage of this method is discouraged, use {_safeMint} whenever possible
         *
         * Requirements:
         *
         * - `tokenId` must not exist.
         * - `to` cannot be the zero address.
         *
         * Emits a {Transfer} event.
         */
        function _mint(address to, uint256 tokenId) internal virtual {
            require(to != address(0), "ERC721: mint to the zero address");
            require(!_exists(tokenId), "ERC721: token already minted");
            _beforeTokenTransfer(address(0), to, tokenId);
            _balances[to] += 1;
            _owners[tokenId] = to;
            emit Transfer(address(0), to, tokenId);
        }
        /**
         * @dev Destroys `tokenId`.
         * The approval is cleared when the token is burned.
         *
         * Requirements:
         *
         * - `tokenId` must exist.
         *
         * Emits a {Transfer} event.
         */
        function _burn(uint256 tokenId) internal virtual {
            address owner = ERC721.ownerOf(tokenId);
            _beforeTokenTransfer(owner, address(0), tokenId);
            // Clear approvals
            _approve(address(0), tokenId);
            _balances[owner] -= 1;
            delete _owners[tokenId];
            emit Transfer(owner, address(0), tokenId);
        }
        /**
         * @dev Transfers `tokenId` from `from` to `to`.
         *  As opposed to {transferFrom}, this imposes no restrictions on msg.sender.
         *
         * Requirements:
         *
         * - `to` cannot be the zero address.
         * - `tokenId` token must be owned by `from`.
         *
         * Emits a {Transfer} event.
         */
        function _transfer(
            address from,
            address to,
            uint256 tokenId
        ) internal virtual {
            require(ERC721.ownerOf(tokenId) == from, "ERC721: transfer of token that is not own");
            require(to != address(0), "ERC721: transfer to the zero address");
            _beforeTokenTransfer(from, to, tokenId);
            // Clear approvals from the previous owner
            _approve(address(0), tokenId);
            _balances[from] -= 1;
            _balances[to] += 1;
            _owners[tokenId] = to;
            emit Transfer(from, to, tokenId);
        }
        /**
         * @dev Approve `to` to operate on `tokenId`
         *
         * Emits a {Approval} event.
         */
        function _approve(address to, uint256 tokenId) internal virtual {
            _tokenApprovals[tokenId] = to;
            emit Approval(ERC721.ownerOf(tokenId), to, tokenId);
        }
        /**
         * @dev Internal function to invoke {IERC721Receiver-onERC721Received} on a target address.
         * The call is not executed if the target address is not a contract.
         *
         * @param from address representing the previous owner of the given token ID
         * @param to target address that will receive the tokens
         * @param tokenId uint256 ID of the token to be transferred
         * @param _data bytes optional data to send along with the call
         * @return bool whether the call correctly returned the expected magic value
         */
        function _checkOnERC721Received(
            address from,
            address to,
            uint256 tokenId,
            bytes memory _data
        ) private returns (bool) {
            if (to.isContract()) {
                try IERC721Receiver(to).onERC721Received(_msgSender(), from, tokenId, _data) returns (bytes4 retval) {
                    return retval == IERC721Receiver.onERC721Received.selector;
                } catch (bytes memory reason) {
                    if (reason.length == 0) {
                        revert("ERC721: transfer to non ERC721Receiver implementer");
                    } else {
                        assembly {
                            revert(add(32, reason), mload(reason))
                        }
                    }
                }
            } else {
                return true;
            }
        }
        /**
         * @dev Hook that is called before any token transfer. This includes minting
         * and burning.
         *
         * Calling conditions:
         *
         * - When `from` and `to` are both non-zero, ``from``'s `tokenId` will be
         * transferred to `to`.
         * - When `from` is zero, `tokenId` will be minted for `to`.
         * - When `to` is zero, ``from``'s `tokenId` will be burned.
         * - `from` and `to` are never both zero.
         *
         * To learn more about hooks, head to xref:ROOT:extending-contracts.adoc#using-hooks[Using Hooks].
         */
        function _beforeTokenTransfer(
            address from,
            address to,
            uint256 tokenId
        ) internal virtual {}
    }
    // SPDX-License-Identifier: MIT
    pragma solidity ^0.8.0;
    import "../utils/Context.sol";
    /**
     * @dev Contract module which provides a basic access control mechanism, where
     * there is an account (an owner) that can be granted exclusive access to
     * specific functions.
     *
     * By default, the owner account will be the one that deploys the contract. This
     * can later be changed with {transferOwnership}.
     *
     * This module is used through inheritance. It will make available the modifier
     * `onlyOwner`, which can be applied to your functions to restrict their use to
     * the owner.
     */
    abstract contract Ownable is Context {
        address private _owner;
        event OwnershipTransferred(address indexed previousOwner, address indexed newOwner);
        /**
         * @dev Initializes the contract setting the deployer as the initial owner.
         */
        constructor() {
            _setOwner(_msgSender());
        }
        /**
         * @dev Returns the address of the current owner.
         */
        function owner() public view virtual returns (address) {
            return _owner;
        }
        /**
         * @dev Throws if called by any account other than the owner.
         */
        modifier onlyOwner() {
            require(owner() == _msgSender(), "Ownable: caller is not the owner");
            _;
        }
        /**
         * @dev Leaves the contract without owner. It will not be possible to call
         * `onlyOwner` functions anymore. Can only be called by the current owner.
         *
         * NOTE: Renouncing ownership will leave the contract without an owner,
         * thereby removing any functionality that is only available to the owner.
         */
        function renounceOwnership() public virtual onlyOwner {
            _setOwner(address(0));
        }
        /**
         * @dev Transfers ownership of the contract to a new account (`newOwner`).
         * Can only be called by the current owner.
         */
        function transferOwnership(address newOwner) public virtual onlyOwner {
            require(newOwner != address(0), "Ownable: new owner is the zero address");
            _setOwner(newOwner);
        }
        function _setOwner(address newOwner) private {
            address oldOwner = _owner;
            _owner = newOwner;
            emit OwnershipTransferred(oldOwner, newOwner);
        }
    }