{"AccessControl.sol":{"content":"// SPDX-License-Identifier: MIT\r\n\r\npragma solidity \u003e=0.6.0 \u003c0.8.0;\r\n\r\nimport \"./EnumerableSet.sol\";\r\nimport \"./Address.sol\";\r\nimport \"./Context.sol\";\r\n\r\n/**\r\n * @dev Contract module that allows children to implement role-based access\r\n * control mechanisms.\r\n *\r\n * Roles are referred to by their `bytes32` identifier. These should be exposed\r\n * in the external API and be unique. The best way to achieve this is by\r\n * using `public constant` hash digests:\r\n *\r\n * ```\r\n * bytes32 public constant MY_ROLE = keccak256(\"MY_ROLE\");\r\n * ```\r\n *\r\n * Roles can be used to represent a set of permissions. To restrict access to a\r\n * function call, use {hasRole}:\r\n *\r\n * ```\r\n * function foo() public {\r\n *     require(hasRole(MY_ROLE, msg.sender));\r\n *     ...\r\n * }\r\n * ```\r\n *\r\n * Roles can be granted and revoked dynamically via the {grantRole} and\r\n * {revokeRole} functions. Each role has an associated admin role, and only\r\n * accounts that have a role\u0027s admin role can call {grantRole} and {revokeRole}.\r\n *\r\n * By default, the admin role for all roles is `DEFAULT_ADMIN_ROLE`, which means\r\n * that only accounts with this role will be able to grant or revoke other\r\n * roles. More complex role relationships can be created by using\r\n * {_setRoleAdmin}.\r\n *\r\n * WARNING: The `DEFAULT_ADMIN_ROLE` is also its own admin: it has permission to\r\n * grant and revoke this role. Extra precautions should be taken to secure\r\n * accounts that have been granted it.\r\n */\r\nabstract contract AccessControl is Context {\r\n    using EnumerableSet for EnumerableSet.AddressSet;\r\n    using Address for address;\r\n\r\n    struct RoleData {\r\n        EnumerableSet.AddressSet members;\r\n        bytes32 adminRole;\r\n    }\r\n\r\n    mapping (bytes32 =\u003e RoleData) private _roles;\r\n\r\n    bytes32 public constant DEFAULT_ADMIN_ROLE = 0x00;\r\n\r\n    /**\r\n     * @dev Emitted when `newAdminRole` is set as ``role``\u0027s admin role, replacing `previousAdminRole`\r\n     *\r\n     * `DEFAULT_ADMIN_ROLE` is the starting admin for all roles, despite\r\n     * {RoleAdminChanged} not being emitted signaling this.\r\n     *\r\n     * _Available since v3.1._\r\n     */\r\n    event RoleAdminChanged(bytes32 indexed role, bytes32 indexed previousAdminRole, bytes32 indexed newAdminRole);\r\n\r\n    /**\r\n     * @dev Emitted when `account` is granted `role`.\r\n     *\r\n     * `sender` is the account that originated the contract call, an admin role\r\n     * bearer except when using {_setupRole}.\r\n     */\r\n    event RoleGranted(bytes32 indexed role, address indexed account, address indexed sender);\r\n\r\n    /**\r\n     * @dev Emitted when `account` is revoked `role`.\r\n     *\r\n     * `sender` is the account that originated the contract call:\r\n     *   - if using `revokeRole`, it is the admin role bearer\r\n     *   - if using `renounceRole`, it is the role bearer (i.e. `account`)\r\n     */\r\n    event RoleRevoked(bytes32 indexed role, address indexed account, address indexed sender);\r\n\r\n    /**\r\n     * @dev Returns `true` if `account` has been granted `role`.\r\n     */\r\n    function hasRole(bytes32 role, address account) public view returns (bool) {\r\n        return _roles[role].members.contains(account);\r\n    }\r\n\r\n    /**\r\n     * @dev Returns the number of accounts that have `role`. Can be used\r\n     * together with {getRoleMember} to enumerate all bearers of a role.\r\n     */\r\n    function getRoleMemberCount(bytes32 role) public view returns (uint256) {\r\n        return _roles[role].members.length();\r\n    }\r\n\r\n    /**\r\n     * @dev Returns one of the accounts that have `role`. `index` must be a\r\n     * value between 0 and {getRoleMemberCount}, non-inclusive.\r\n     *\r\n     * Role bearers are not sorted in any particular way, and their ordering may\r\n     * change at any point.\r\n     *\r\n     * WARNING: When using {getRoleMember} and {getRoleMemberCount}, make sure\r\n     * you perform all queries on the same block. See the following\r\n     * https://forum.openzeppelin.com/t/iterating-over-elements-on-enumerableset-in-openzeppelin-contracts/2296[forum post]\r\n     * for more information.\r\n     */\r\n    function getRoleMember(bytes32 role, uint256 index) public view returns (address) {\r\n        return _roles[role].members.at(index);\r\n    }\r\n\r\n    /**\r\n     * @dev Returns the admin role that controls `role`. See {grantRole} and\r\n     * {revokeRole}.\r\n     *\r\n     * To change a role\u0027s admin, use {_setRoleAdmin}.\r\n     */\r\n    function getRoleAdmin(bytes32 role) public view returns (bytes32) {\r\n        return _roles[role].adminRole;\r\n    }\r\n\r\n    /**\r\n     * @dev Grants `role` to `account`.\r\n     *\r\n     * If `account` had not been already granted `role`, emits a {RoleGranted}\r\n     * event.\r\n     *\r\n     * Requirements:\r\n     *\r\n     * - the caller must have ``role``\u0027s admin role.\r\n     */\r\n    function grantRole(bytes32 role, address account) public virtual {\r\n        require(hasRole(_roles[role].adminRole, _msgSender()), \"AccessControl: sender must be an admin to grant\");\r\n\r\n        _grantRole(role, account);\r\n    }\r\n\r\n    /**\r\n     * @dev Revokes `role` from `account`.\r\n     *\r\n     * If `account` had been granted `role`, emits a {RoleRevoked} event.\r\n     *\r\n     * Requirements:\r\n     *\r\n     * - the caller must have ``role``\u0027s admin role.\r\n     */\r\n    function revokeRole(bytes32 role, address account) public virtual {\r\n        require(hasRole(_roles[role].adminRole, _msgSender()), \"AccessControl: sender must be an admin to revoke\");\r\n\r\n        _revokeRole(role, account);\r\n    }\r\n\r\n    /**\r\n     * @dev Revokes `role` from the calling account.\r\n     *\r\n     * Roles are often managed via {grantRole} and {revokeRole}: this function\u0027s\r\n     * purpose is to provide a mechanism for accounts to lose their privileges\r\n     * if they are compromised (such as when a trusted device is misplaced).\r\n     *\r\n     * If the calling account had been granted `role`, emits a {RoleRevoked}\r\n     * event.\r\n     *\r\n     * Requirements:\r\n     *\r\n     * - the caller must be `account`.\r\n     */\r\n    function renounceRole(bytes32 role, address account) public virtual {\r\n        require(account == _msgSender(), \"AccessControl: can only renounce roles for self\");\r\n\r\n        _revokeRole(role, account);\r\n    }\r\n\r\n    /**\r\n     * @dev Grants `role` to `account`.\r\n     *\r\n     * If `account` had not been already granted `role`, emits a {RoleGranted}\r\n     * event. Note that unlike {grantRole}, this function doesn\u0027t perform any\r\n     * checks on the calling account.\r\n     *\r\n     * [WARNING]\r\n     * ====\r\n     * This function should only be called from the constructor when setting\r\n     * up the initial roles for the system.\r\n     *\r\n     * Using this function in any other way is effectively circumventing the admin\r\n     * system imposed by {AccessControl}.\r\n     * ====\r\n     */\r\n    function _setupRole(bytes32 role, address account) internal virtual {\r\n        _grantRole(role, account);\r\n    }\r\n\r\n    /**\r\n     * @dev Sets `adminRole` as ``role``\u0027s admin role.\r\n     *\r\n     * Emits a {RoleAdminChanged} event.\r\n     */\r\n    function _setRoleAdmin(bytes32 role, bytes32 adminRole) internal virtual {\r\n        emit RoleAdminChanged(role, _roles[role].adminRole, adminRole);\r\n        _roles[role].adminRole = adminRole;\r\n    }\r\n\r\n    function _grantRole(bytes32 role, address account) private {\r\n        if (_roles[role].members.add(account)) {\r\n            emit RoleGranted(role, account, _msgSender());\r\n        }\r\n    }\r\n\r\n    function _revokeRole(bytes32 role, address account) private {\r\n        if (_roles[role].members.remove(account)) {\r\n            emit RoleRevoked(role, account, _msgSender());\r\n        }\r\n    }\r\n}"},"Address.sol":{"content":"// SPDX-License-Identifier: MIT\r\n\r\npragma solidity \u003e=0.6.2 \u003c0.8.0;\r\n\r\n/**\r\n * @dev Collection of functions related to the address type\r\n */\r\nlibrary Address {\r\n    /**\r\n     * @dev Returns true if `account` is a contract.\r\n     *\r\n     * [IMPORTANT]\r\n     * ====\r\n     * It is unsafe to assume that an address for which this function returns\r\n     * false is an externally-owned account (EOA) and not a contract.\r\n     *\r\n     * Among others, `isContract` will return false for the following\r\n     * types of addresses:\r\n     *\r\n     *  - an externally-owned account\r\n     *  - a contract in construction\r\n     *  - an address where a contract will be created\r\n     *  - an address where a contract lived, but was destroyed\r\n     * ====\r\n     */\r\n    function isContract(address account) internal view returns (bool) {\r\n        // This method relies on extcodesize, which returns 0 for contracts in\r\n        // construction, since the code is only stored at the end of the\r\n        // constructor execution.\r\n\r\n        uint256 size;\r\n        // solhint-disable-next-line no-inline-assembly\r\n        assembly { size := extcodesize(account) }\r\n        return size \u003e 0;\r\n    }\r\n\r\n    /**\r\n     * @dev Replacement for Solidity\u0027s `transfer`: sends `amount` wei to\r\n     * `recipient`, forwarding all available gas and reverting on errors.\r\n     *\r\n     * https://eips.ethereum.org/EIPS/eip-1884[EIP1884] increases the gas cost\r\n     * of certain opcodes, possibly making contracts go over the 2300 gas limit\r\n     * imposed by `transfer`, making them unable to receive funds via\r\n     * `transfer`. {sendValue} removes this limitation.\r\n     *\r\n     * https://diligence.consensys.net/posts/2019/09/stop-using-soliditys-transfer-now/[Learn more].\r\n     *\r\n     * IMPORTANT: because control is transferred to `recipient`, care must be\r\n     * taken to not create reentrancy vulnerabilities. Consider using\r\n     * {ReentrancyGuard} or the\r\n     * https://solidity.readthedocs.io/en/v0.5.11/security-considerations.html#use-the-checks-effects-interactions-pattern[checks-effects-interactions pattern].\r\n     */\r\n    function sendValue(address payable recipient, uint256 amount) internal {\r\n        require(address(this).balance \u003e= amount, \"Address: insufficient balance\");\r\n\r\n        // solhint-disable-next-line avoid-low-level-calls, avoid-call-value\r\n        (bool success, ) = recipient.call{ value: amount }(\"\");\r\n        require(success, \"Address: unable to send value, recipient may have reverted\");\r\n    }\r\n\r\n    /**\r\n     * @dev Performs a Solidity function call using a low level `call`. A\r\n     * plain`call` is an unsafe replacement for a function call: use this\r\n     * function instead.\r\n     *\r\n     * If `target` reverts with a revert reason, it is bubbled up by this\r\n     * function (like regular Solidity function calls).\r\n     *\r\n     * Returns the raw returned data. To convert to the expected return value,\r\n     * use https://solidity.readthedocs.io/en/latest/units-and-global-variables.html?highlight=abi.decode#abi-encoding-and-decoding-functions[`abi.decode`].\r\n     *\r\n     * Requirements:\r\n     *\r\n     * - `target` must be a contract.\r\n     * - calling `target` with `data` must not revert.\r\n     *\r\n     * _Available since v3.1._\r\n     */\r\n    function functionCall(address target, bytes memory data) internal returns (bytes memory) {\r\n      return functionCall(target, data, \"Address: low-level call failed\");\r\n    }\r\n\r\n    /**\r\n     * @dev Same as {xref-Address-functionCall-address-bytes-}[`functionCall`], but with\r\n     * `errorMessage` as a fallback revert reason when `target` reverts.\r\n     *\r\n     * _Available since v3.1._\r\n     */\r\n    function functionCall(address target, bytes memory data, string memory errorMessage) internal returns (bytes memory) {\r\n        return functionCallWithValue(target, data, 0, errorMessage);\r\n    }\r\n\r\n    /**\r\n     * @dev Same as {xref-Address-functionCall-address-bytes-}[`functionCall`],\r\n     * but also transferring `value` wei to `target`.\r\n     *\r\n     * Requirements:\r\n     *\r\n     * - the calling contract must have an ETH balance of at least `value`.\r\n     * - the called Solidity function must be `payable`.\r\n     *\r\n     * _Available since v3.1._\r\n     */\r\n    function functionCallWithValue(address target, bytes memory data, uint256 value) internal returns (bytes memory) {\r\n        return functionCallWithValue(target, data, value, \"Address: low-level call with value failed\");\r\n    }\r\n\r\n    /**\r\n     * @dev Same as {xref-Address-functionCallWithValue-address-bytes-uint256-}[`functionCallWithValue`], but\r\n     * with `errorMessage` as a fallback revert reason when `target` reverts.\r\n     *\r\n     * _Available since v3.1._\r\n     */\r\n    function functionCallWithValue(address target, bytes memory data, uint256 value, string memory errorMessage) internal returns (bytes memory) {\r\n        require(address(this).balance \u003e= value, \"Address: insufficient balance for call\");\r\n        require(isContract(target), \"Address: call to non-contract\");\r\n\r\n        // solhint-disable-next-line avoid-low-level-calls\r\n        (bool success, bytes memory returndata) = target.call{ value: value }(data);\r\n        return _verifyCallResult(success, returndata, errorMessage);\r\n    }\r\n\r\n    /**\r\n     * @dev Same as {xref-Address-functionCall-address-bytes-}[`functionCall`],\r\n     * but performing a static call.\r\n     *\r\n     * _Available since v3.3._\r\n     */\r\n    function functionStaticCall(address target, bytes memory data) internal view returns (bytes memory) {\r\n        return functionStaticCall(target, data, \"Address: low-level static call failed\");\r\n    }\r\n\r\n    /**\r\n     * @dev Same as {xref-Address-functionCall-address-bytes-string-}[`functionCall`],\r\n     * but performing a static call.\r\n     *\r\n     * _Available since v3.3._\r\n     */\r\n    function functionStaticCall(address target, bytes memory data, string memory errorMessage) internal view returns (bytes memory) {\r\n        require(isContract(target), \"Address: static call to non-contract\");\r\n\r\n        // solhint-disable-next-line avoid-low-level-calls\r\n        (bool success, bytes memory returndata) = target.staticcall(data);\r\n        return _verifyCallResult(success, returndata, errorMessage);\r\n    }\r\n\r\n    /**\r\n     * @dev Same as {xref-Address-functionCall-address-bytes-}[`functionCall`],\r\n     * but performing a delegate call.\r\n     *\r\n     * _Available since v3.3._\r\n     */\r\n    function functionDelegateCall(address target, bytes memory data) internal returns (bytes memory) {\r\n        return functionDelegateCall(target, data, \"Address: low-level delegate call failed\");\r\n    }\r\n\r\n    /**\r\n     * @dev Same as {xref-Address-functionCall-address-bytes-string-}[`functionCall`],\r\n     * but performing a delegate call.\r\n     *\r\n     * _Available since v3.3._\r\n     */\r\n    function functionDelegateCall(address target, bytes memory data, string memory errorMessage) internal returns (bytes memory) {\r\n        require(isContract(target), \"Address: delegate call to non-contract\");\r\n\r\n        // solhint-disable-next-line avoid-low-level-calls\r\n        (bool success, bytes memory returndata) = target.delegatecall(data);\r\n        return _verifyCallResult(success, returndata, errorMessage);\r\n    }\r\n\r\n    function _verifyCallResult(bool success, bytes memory returndata, string memory errorMessage) private pure returns(bytes memory) {\r\n        if (success) {\r\n            return returndata;\r\n        } else {\r\n            // Look for revert reason and bubble it up if present\r\n            if (returndata.length \u003e 0) {\r\n                // The easiest way to bubble the revert reason is using memory via assembly\r\n\r\n                // solhint-disable-next-line no-inline-assembly\r\n                assembly {\r\n                    let returndata_size := mload(returndata)\r\n                    revert(add(32, returndata), returndata_size)\r\n                }\r\n            } else {\r\n                revert(errorMessage);\r\n            }\r\n        }\r\n    }\r\n}"},"coinbase.sol":{"content":"//Be name khoda\r\n\r\n//SPDX-License-Identifier: MIT\r\n//Thank you DEA...\r\n/* \r\n\r\n  ██████╗ ██████╗ ██╗███╗   ██╗██████╗  █████╗ ███████╗███████╗    ██╗██████╗  ██████╗ \r\n██╔════╝██╔═══██╗██║████╗  ██║██╔══██╗██╔══██╗██╔════╝██╔════╝    ██║██╔══██╗██╔═══██╗\r\n██║     ██║   ██║██║██╔██╗ ██║██████╔╝███████║███████╗█████╗      ██║██████╔╝██║   ██║\r\n██║     ██║   ██║██║██║╚██╗██║██╔══██╗██╔══██║╚════██║██╔══╝      ██║██╔═══╝ ██║   ██║\r\n╚██████╗╚██████╔╝██║██║ ╚████║██████╔╝██║  ██║███████║███████╗    ██║██║     ╚██████╔╝\r\n ╚═════╝ ╚═════╝ ╚═╝╚═╝  ╚═══╝╚═════╝ ╚═╝  ╚═╝╚══════╝╚══════╝    ╚═╝╚═╝      ╚═════╝ \r\n            \r\n*/                                                                           \r\n\r\n\r\npragma solidity ^0.6.12;\r\n\r\nimport \"./AccessControl.sol\";\r\nimport \"./ERC20.sol\";\r\n\r\ncontract CoinbaseFutureToken is ERC20, AccessControl{\r\n\r\n\t\r\n\r\n\tbytes32 public constant MINTER_ROLE = keccak256(\"MINTER_ROLE\");\r\n\tbytes32 public constant BURNER_ROLE = keccak256(\"BURNER_ROLE\");\r\n\t\r\n\r\n\tconstructor() public ERC20(\"DEUS Synthetic Coinbase IOU\", \"wCOINBASE-IOU\") {\r\n\t\t_setupRole(DEFAULT_ADMIN_ROLE, msg.sender);\t\r\n\t}\r\n\r\n\tfunction mint(address to, uint256 amount) public {\r\n        // Check that the calling account has the minter role\r\n        require(hasRole(MINTER_ROLE, msg.sender), \"Caller is not a minter\");\r\n        _mint(to, amount);\r\n    }\r\n\r\n\tfunction burn(address from, uint256 amount) public {\r\n        require(hasRole(BURNER_ROLE, msg.sender), \"Caller is not a burner\");\r\n        _burn(from, amount);\r\n    }\r\n\r\n\r\n}\r\n\r\n//...and thank you DEUS.\r\n//Dar panah khoda"},"Context.sol":{"content":"// SPDX-License-Identifier: MIT\r\n\r\npragma solidity \u003e=0.6.0 \u003c0.8.0;\r\n\r\n/*\r\n * @dev Provides information about the current execution context, including the\r\n * sender of the transaction and its data. While these are generally available\r\n * via msg.sender and msg.data, they should not be accessed in such a direct\r\n * manner, since when dealing with GSN meta-transactions the account sending and\r\n * paying for execution may not be the actual sender (as far as an application\r\n * is concerned).\r\n *\r\n * This contract is only required for intermediate, library-like contracts.\r\n */\r\nabstract contract Context {\r\n    function _msgSender() internal view virtual returns (address payable) {\r\n        return msg.sender;\r\n    }\r\n\r\n    function _msgData() internal view virtual returns (bytes memory) {\r\n        this; // silence state mutability warning without generating bytecode - see https://github.com/ethereum/solidity/issues/2691\r\n        return msg.data;\r\n    }\r\n}"},"EnumerableSet.sol":{"content":"// SPDX-License-Identifier: MIT\r\n\r\npragma solidity \u003e=0.6.0 \u003c0.8.0;\r\n\r\n/**\r\n * @dev Library for managing\r\n * https://en.wikipedia.org/wiki/Set_(abstract_data_type)[sets] of primitive\r\n * types.\r\n *\r\n * Sets have the following properties:\r\n *\r\n * - Elements are added, removed, and checked for existence in constant time\r\n * (O(1)).\r\n * - Elements are enumerated in O(n). No guarantees are made on the ordering.\r\n *\r\n * ```\r\n * contract Example {\r\n *     // Add the library methods\r\n *     using EnumerableSet for EnumerableSet.AddressSet;\r\n *\r\n *     // Declare a set state variable\r\n *     EnumerableSet.AddressSet private mySet;\r\n * }\r\n * ```\r\n *\r\n * As of v3.3.0, sets of type `bytes32` (`Bytes32Set`), `address` (`AddressSet`)\r\n * and `uint256` (`UintSet`) are supported.\r\n */\r\nlibrary EnumerableSet {\r\n    // To implement this library for multiple types with as little code\r\n    // repetition as possible, we write it in terms of a generic Set type with\r\n    // bytes32 values.\r\n    // The Set implementation uses private functions, and user-facing\r\n    // implementations (such as AddressSet) are just wrappers around the\r\n    // underlying Set.\r\n    // This means that we can only create new EnumerableSets for types that fit\r\n    // in bytes32.\r\n\r\n    struct Set {\r\n        // Storage of set values\r\n        bytes32[] _values;\r\n\r\n        // Position of the value in the `values` array, plus 1 because index 0\r\n        // means a value is not in the set.\r\n        mapping (bytes32 =\u003e uint256) _indexes;\r\n    }\r\n\r\n    /**\r\n     * @dev Add a value to a set. O(1).\r\n     *\r\n     * Returns true if the value was added to the set, that is if it was not\r\n     * already present.\r\n     */\r\n    function _add(Set storage set, bytes32 value) private returns (bool) {\r\n        if (!_contains(set, value)) {\r\n            set._values.push(value);\r\n            // The value is stored at length-1, but we add 1 to all indexes\r\n            // and use 0 as a sentinel value\r\n            set._indexes[value] = set._values.length;\r\n            return true;\r\n        } else {\r\n            return false;\r\n        }\r\n    }\r\n\r\n    /**\r\n     * @dev Removes a value from a set. O(1).\r\n     *\r\n     * Returns true if the value was removed from the set, that is if it was\r\n     * present.\r\n     */\r\n    function _remove(Set storage set, bytes32 value) private returns (bool) {\r\n        // We read and store the value\u0027s index to prevent multiple reads from the same storage slot\r\n        uint256 valueIndex = set._indexes[value];\r\n\r\n        if (valueIndex != 0) { // Equivalent to contains(set, value)\r\n            // To delete an element from the _values array in O(1), we swap the element to delete with the last one in\r\n            // the array, and then remove the last element (sometimes called as \u0027swap and pop\u0027).\r\n            // This modifies the order of the array, as noted in {at}.\r\n\r\n            uint256 toDeleteIndex = valueIndex - 1;\r\n            uint256 lastIndex = set._values.length - 1;\r\n\r\n            // When the value to delete is the last one, the swap operation is unnecessary. However, since this occurs\r\n            // so rarely, we still do the swap anyway to avoid the gas cost of adding an \u0027if\u0027 statement.\r\n\r\n            bytes32 lastvalue = set._values[lastIndex];\r\n\r\n            // Move the last value to the index where the value to delete is\r\n            set._values[toDeleteIndex] = lastvalue;\r\n            // Update the index for the moved value\r\n            set._indexes[lastvalue] = toDeleteIndex + 1; // All indexes are 1-based\r\n\r\n            // Delete the slot where the moved value was stored\r\n            set._values.pop();\r\n\r\n            // Delete the index for the deleted slot\r\n            delete set._indexes[value];\r\n\r\n            return true;\r\n        } else {\r\n            return false;\r\n        }\r\n    }\r\n\r\n    /**\r\n     * @dev Returns true if the value is in the set. O(1).\r\n     */\r\n    function _contains(Set storage set, bytes32 value) private view returns (bool) {\r\n        return set._indexes[value] != 0;\r\n    }\r\n\r\n    /**\r\n     * @dev Returns the number of values on the set. O(1).\r\n     */\r\n    function _length(Set storage set) private view returns (uint256) {\r\n        return set._values.length;\r\n    }\r\n\r\n   /**\r\n    * @dev Returns the value stored at position `index` in the set. O(1).\r\n    *\r\n    * Note that there are no guarantees on the ordering of values inside the\r\n    * array, and it may change when more values are added or removed.\r\n    *\r\n    * Requirements:\r\n    *\r\n    * - `index` must be strictly less than {length}.\r\n    */\r\n    function _at(Set storage set, uint256 index) private view returns (bytes32) {\r\n        require(set._values.length \u003e index, \"EnumerableSet: index out of bounds\");\r\n        return set._values[index];\r\n    }\r\n\r\n    // Bytes32Set\r\n\r\n    struct Bytes32Set {\r\n        Set _inner;\r\n    }\r\n\r\n    /**\r\n     * @dev Add a value to a set. O(1).\r\n     *\r\n     * Returns true if the value was added to the set, that is if it was not\r\n     * already present.\r\n     */\r\n    function add(Bytes32Set storage set, bytes32 value) internal returns (bool) {\r\n        return _add(set._inner, value);\r\n    }\r\n\r\n    /**\r\n     * @dev Removes a value from a set. O(1).\r\n     *\r\n     * Returns true if the value was removed from the set, that is if it was\r\n     * present.\r\n     */\r\n    function remove(Bytes32Set storage set, bytes32 value) internal returns (bool) {\r\n        return _remove(set._inner, value);\r\n    }\r\n\r\n    /**\r\n     * @dev Returns true if the value is in the set. O(1).\r\n     */\r\n    function contains(Bytes32Set storage set, bytes32 value) internal view returns (bool) {\r\n        return _contains(set._inner, value);\r\n    }\r\n\r\n    /**\r\n     * @dev Returns the number of values in the set. O(1).\r\n     */\r\n    function length(Bytes32Set storage set) internal view returns (uint256) {\r\n        return _length(set._inner);\r\n    }\r\n\r\n   /**\r\n    * @dev Returns the value stored at position `index` in the set. O(1).\r\n    *\r\n    * Note that there are no guarantees on the ordering of values inside the\r\n    * array, and it may change when more values are added or removed.\r\n    *\r\n    * Requirements:\r\n    *\r\n    * - `index` must be strictly less than {length}.\r\n    */\r\n    function at(Bytes32Set storage set, uint256 index) internal view returns (bytes32) {\r\n        return _at(set._inner, index);\r\n    }\r\n\r\n    // AddressSet\r\n\r\n    struct AddressSet {\r\n        Set _inner;\r\n    }\r\n\r\n    /**\r\n     * @dev Add a value to a set. O(1).\r\n     *\r\n     * Returns true if the value was added to the set, that is if it was not\r\n     * already present.\r\n     */\r\n    function add(AddressSet storage set, address value) internal returns (bool) {\r\n        return _add(set._inner, bytes32(uint256(uint160(value))));\r\n    }\r\n\r\n    /**\r\n     * @dev Removes a value from a set. O(1).\r\n     *\r\n     * Returns true if the value was removed from the set, that is if it was\r\n     * present.\r\n     */\r\n    function remove(AddressSet storage set, address value) internal returns (bool) {\r\n        return _remove(set._inner, bytes32(uint256(uint160(value))));\r\n    }\r\n\r\n    /**\r\n     * @dev Returns true if the value is in the set. O(1).\r\n     */\r\n    function contains(AddressSet storage set, address value) internal view returns (bool) {\r\n        return _contains(set._inner, bytes32(uint256(uint160(value))));\r\n    }\r\n\r\n    /**\r\n     * @dev Returns the number of values in the set. O(1).\r\n     */\r\n    function length(AddressSet storage set) internal view returns (uint256) {\r\n        return _length(set._inner);\r\n    }\r\n\r\n   /**\r\n    * @dev Returns the value stored at position `index` in the set. O(1).\r\n    *\r\n    * Note that there are no guarantees on the ordering of values inside the\r\n    * array, and it may change when more values are added or removed.\r\n    *\r\n    * Requirements:\r\n    *\r\n    * - `index` must be strictly less than {length}.\r\n    */\r\n    function at(AddressSet storage set, uint256 index) internal view returns (address) {\r\n        return address(uint160(uint256(_at(set._inner, index))));\r\n    }\r\n\r\n\r\n    // UintSet\r\n\r\n    struct UintSet {\r\n        Set _inner;\r\n    }\r\n\r\n    /**\r\n     * @dev Add a value to a set. O(1).\r\n     *\r\n     * Returns true if the value was added to the set, that is if it was not\r\n     * already present.\r\n     */\r\n    function add(UintSet storage set, uint256 value) internal returns (bool) {\r\n        return _add(set._inner, bytes32(value));\r\n    }\r\n\r\n    /**\r\n     * @dev Removes a value from a set. O(1).\r\n     *\r\n     * Returns true if the value was removed from the set, that is if it was\r\n     * present.\r\n     */\r\n    function remove(UintSet storage set, uint256 value) internal returns (bool) {\r\n        return _remove(set._inner, bytes32(value));\r\n    }\r\n\r\n    /**\r\n     * @dev Returns true if the value is in the set. O(1).\r\n     */\r\n    function contains(UintSet storage set, uint256 value) internal view returns (bool) {\r\n        return _contains(set._inner, bytes32(value));\r\n    }\r\n\r\n    /**\r\n     * @dev Returns the number of values on the set. O(1).\r\n     */\r\n    function length(UintSet storage set) internal view returns (uint256) {\r\n        return _length(set._inner);\r\n    }\r\n\r\n   /**\r\n    * @dev Returns the value stored at position `index` in the set. O(1).\r\n    *\r\n    * Note that there are no guarantees on the ordering of values inside the\r\n    * array, and it may change when more values are added or removed.\r\n    *\r\n    * Requirements:\r\n    *\r\n    * - `index` must be strictly less than {length}.\r\n    */\r\n    function at(UintSet storage set, uint256 index) internal view returns (uint256) {\r\n        return uint256(_at(set._inner, index));\r\n    }\r\n}"},"ERC20.sol":{"content":"// SPDX-License-Identifier: MIT\r\n\r\npragma solidity \u003e=0.6.0 \u003c0.8.0;\r\n\r\nimport \"./Context.sol\";\r\nimport \"./IERC20.sol\";\r\nimport \"./SafeMath.sol\";\r\n\r\n/**\r\n * @dev Implementation of the {IERC20} interface.\r\n *\r\n * This implementation is agnostic to the way tokens are created. This means\r\n * that a supply mechanism has to be added in a derived contract using {_mint}.\r\n * For a generic mechanism see {ERC20PresetMinterPauser}.\r\n *\r\n * TIP: For a detailed writeup see our guide\r\n * https://forum.zeppelin.solutions/t/how-to-implement-erc20-supply-mechanisms/226[How\r\n * to implement supply mechanisms].\r\n *\r\n * We have followed general OpenZeppelin guidelines: functions revert instead\r\n * of returning `false` on failure. This behavior is nonetheless conventional\r\n * and does not conflict with the expectations of ERC20 applications.\r\n *\r\n * Additionally, an {Approval} event is emitted on calls to {transferFrom}.\r\n * This allows applications to reconstruct the allowance for all accounts just\r\n * by listening to said events. Other implementations of the EIP may not emit\r\n * these events, as it isn\u0027t required by the specification.\r\n *\r\n * Finally, the non-standard {decreaseAllowance} and {increaseAllowance}\r\n * functions have been added to mitigate the well-known issues around setting\r\n * allowances. See {IERC20-approve}.\r\n */\r\ncontract ERC20 is Context, IERC20 {\r\n    using SafeMath for uint256;\r\n\r\n    mapping (address =\u003e uint256) private _balances;\r\n\r\n    mapping (address =\u003e mapping (address =\u003e uint256)) private _allowances;\r\n\r\n    uint256 private _totalSupply;\r\n\r\n    string private _name;\r\n    string private _symbol;\r\n    uint8 private _decimals;\r\n\r\n    /**\r\n     * @dev Sets the values for {name} and {symbol}, initializes {decimals} with\r\n     * a default value of 18.\r\n     *\r\n     * To select a different value for {decimals}, use {_setupDecimals}.\r\n     *\r\n     * All three of these values are immutable: they can only be set once during\r\n     * construction.\r\n     */\r\n    constructor (string memory name_, string memory symbol_) public {\r\n        _name = name_;\r\n        _symbol = symbol_;\r\n        _decimals = 18;\r\n    }\r\n\r\n    /**\r\n     * @dev Returns the name of the token.\r\n     */\r\n    function name() public view returns (string memory) {\r\n        return _name;\r\n    }\r\n\r\n    /**\r\n     * @dev Returns the symbol of the token, usually a shorter version of the\r\n     * name.\r\n     */\r\n    function symbol() public view returns (string memory) {\r\n        return _symbol;\r\n    }\r\n\r\n    /**\r\n     * @dev Returns the number of decimals used to get its user representation.\r\n     * For example, if `decimals` equals `2`, a balance of `505` tokens should\r\n     * be displayed to a user as `5,05` (`505 / 10 ** 2`).\r\n     *\r\n     * Tokens usually opt for a value of 18, imitating the relationship between\r\n     * Ether and Wei. This is the value {ERC20} uses, unless {_setupDecimals} is\r\n     * called.\r\n     *\r\n     * NOTE: This information is only used for _display_ purposes: it in\r\n     * no way affects any of the arithmetic of the contract, including\r\n     * {IERC20-balanceOf} and {IERC20-transfer}.\r\n     */\r\n    function decimals() public view returns (uint8) {\r\n        return _decimals;\r\n    }\r\n\r\n    /**\r\n     * @dev See {IERC20-totalSupply}.\r\n     */\r\n    function totalSupply() public view override returns (uint256) {\r\n        return _totalSupply;\r\n    }\r\n\r\n    /**\r\n     * @dev See {IERC20-balanceOf}.\r\n     */\r\n    function balanceOf(address account) public view override returns (uint256) {\r\n        return _balances[account];\r\n    }\r\n\r\n    /**\r\n     * @dev See {IERC20-transfer}.\r\n     *\r\n     * Requirements:\r\n     *\r\n     * - `recipient` cannot be the zero address.\r\n     * - the caller must have a balance of at least `amount`.\r\n     */\r\n    function transfer(address recipient, uint256 amount) public virtual override returns (bool) {\r\n        _transfer(_msgSender(), recipient, amount);\r\n        return true;\r\n    }\r\n\r\n    /**\r\n     * @dev See {IERC20-allowance}.\r\n     */\r\n    function allowance(address owner, address spender) public view virtual override returns (uint256) {\r\n        return _allowances[owner][spender];\r\n    }\r\n\r\n    /**\r\n     * @dev See {IERC20-approve}.\r\n     *\r\n     * Requirements:\r\n     *\r\n     * - `spender` cannot be the zero address.\r\n     */\r\n    function approve(address spender, uint256 amount) public virtual override returns (bool) {\r\n        _approve(_msgSender(), spender, amount);\r\n        return true;\r\n    }\r\n\r\n    /**\r\n     * @dev See {IERC20-transferFrom}.\r\n     *\r\n     * Emits an {Approval} event indicating the updated allowance. This is not\r\n     * required by the EIP. See the note at the beginning of {ERC20}.\r\n     *\r\n     * Requirements:\r\n     *\r\n     * - `sender` and `recipient` cannot be the zero address.\r\n     * - `sender` must have a balance of at least `amount`.\r\n     * - the caller must have allowance for ``sender``\u0027s tokens of at least\r\n     * `amount`.\r\n     */\r\n    function transferFrom(address sender, address recipient, uint256 amount) public virtual override returns (bool) {\r\n        _transfer(sender, recipient, amount);\r\n        _approve(sender, _msgSender(), _allowances[sender][_msgSender()].sub(amount, \"ERC20: transfer amount exceeds allowance\"));\r\n        return true;\r\n    }\r\n\r\n    /**\r\n     * @dev Atomically increases the allowance granted to `spender` by the caller.\r\n     *\r\n     * This is an alternative to {approve} that can be used as a mitigation for\r\n     * problems described in {IERC20-approve}.\r\n     *\r\n     * Emits an {Approval} event indicating the updated allowance.\r\n     *\r\n     * Requirements:\r\n     *\r\n     * - `spender` cannot be the zero address.\r\n     */\r\n    function increaseAllowance(address spender, uint256 addedValue) public virtual returns (bool) {\r\n        _approve(_msgSender(), spender, _allowances[_msgSender()][spender].add(addedValue));\r\n        return true;\r\n    }\r\n\r\n    /**\r\n     * @dev Atomically decreases the allowance granted to `spender` by the caller.\r\n     *\r\n     * This is an alternative to {approve} that can be used as a mitigation for\r\n     * problems described in {IERC20-approve}.\r\n     *\r\n     * Emits an {Approval} event indicating the updated allowance.\r\n     *\r\n     * Requirements:\r\n     *\r\n     * - `spender` cannot be the zero address.\r\n     * - `spender` must have allowance for the caller of at least\r\n     * `subtractedValue`.\r\n     */\r\n    function decreaseAllowance(address spender, uint256 subtractedValue) public virtual returns (bool) {\r\n        _approve(_msgSender(), spender, _allowances[_msgSender()][spender].sub(subtractedValue, \"ERC20: decreased allowance below zero\"));\r\n        return true;\r\n    }\r\n\r\n    /**\r\n     * @dev Moves tokens `amount` from `sender` to `recipient`.\r\n     *\r\n     * This is internal function is equivalent to {transfer}, and can be used to\r\n     * e.g. implement automatic token fees, slashing mechanisms, etc.\r\n     *\r\n     * Emits a {Transfer} event.\r\n     *\r\n     * Requirements:\r\n     *\r\n     * - `sender` cannot be the zero address.\r\n     * - `recipient` cannot be the zero address.\r\n     * - `sender` must have a balance of at least `amount`.\r\n     */\r\n    function _transfer(address sender, address recipient, uint256 amount) internal virtual {\r\n        require(sender != address(0), \"ERC20: transfer from the zero address\");\r\n        require(recipient != address(0), \"ERC20: transfer to the zero address\");\r\n\r\n        _beforeTokenTransfer(sender, recipient, amount);\r\n\r\n        _balances[sender] = _balances[sender].sub(amount, \"ERC20: transfer amount exceeds balance\");\r\n        _balances[recipient] = _balances[recipient].add(amount);\r\n        emit Transfer(sender, recipient, amount);\r\n    }\r\n\r\n    /** @dev Creates `amount` tokens and assigns them to `account`, increasing\r\n     * the total supply.\r\n     *\r\n     * Emits a {Transfer} event with `from` set to the zero address.\r\n     *\r\n     * Requirements:\r\n     *\r\n     * - `to` cannot be the zero address.\r\n     */\r\n    function _mint(address account, uint256 amount) internal virtual {\r\n        require(account != address(0), \"ERC20: mint to the zero address\");\r\n\r\n        _beforeTokenTransfer(address(0), account, amount);\r\n\r\n        _totalSupply = _totalSupply.add(amount);\r\n        _balances[account] = _balances[account].add(amount);\r\n        emit Transfer(address(0), account, amount);\r\n    }\r\n\r\n    /**\r\n     * @dev Destroys `amount` tokens from `account`, reducing the\r\n     * total supply.\r\n     *\r\n     * Emits a {Transfer} event with `to` set to the zero address.\r\n     *\r\n     * Requirements:\r\n     *\r\n     * - `account` cannot be the zero address.\r\n     * - `account` must have at least `amount` tokens.\r\n     */\r\n    function _burn(address account, uint256 amount) internal virtual {\r\n        require(account != address(0), \"ERC20: burn from the zero address\");\r\n\r\n        _beforeTokenTransfer(account, address(0), amount);\r\n\r\n        _balances[account] = _balances[account].sub(amount, \"ERC20: burn amount exceeds balance\");\r\n        _totalSupply = _totalSupply.sub(amount);\r\n        emit Transfer(account, address(0), amount);\r\n    }\r\n\r\n    /**\r\n     * @dev Sets `amount` as the allowance of `spender` over the `owner` s tokens.\r\n     *\r\n     * This internal function is equivalent to `approve`, and can be used to\r\n     * e.g. set automatic allowances for certain subsystems, etc.\r\n     *\r\n     * Emits an {Approval} event.\r\n     *\r\n     * Requirements:\r\n     *\r\n     * - `owner` cannot be the zero address.\r\n     * - `spender` cannot be the zero address.\r\n     */\r\n    function _approve(address owner, address spender, uint256 amount) internal virtual {\r\n        require(owner != address(0), \"ERC20: approve from the zero address\");\r\n        require(spender != address(0), \"ERC20: approve to the zero address\");\r\n\r\n        _allowances[owner][spender] = amount;\r\n        emit Approval(owner, spender, amount);\r\n    }\r\n\r\n    /**\r\n     * @dev Sets {decimals} to a value other than the default one of 18.\r\n     *\r\n     * WARNING: This function should only be called from the constructor. Most\r\n     * applications that interact with token contracts will not expect\r\n     * {decimals} to ever change, and may work incorrectly if it does.\r\n     */\r\n    function _setupDecimals(uint8 decimals_) internal {\r\n        _decimals = decimals_;\r\n    }\r\n\r\n    /**\r\n     * @dev Hook that is called before any transfer of tokens. This includes\r\n     * minting and burning.\r\n     *\r\n     * Calling conditions:\r\n     *\r\n     * - when `from` and `to` are both non-zero, `amount` of ``from``\u0027s tokens\r\n     * will be to transferred to `to`.\r\n     * - when `from` is zero, `amount` tokens will be minted for `to`.\r\n     * - when `to` is zero, `amount` of ``from``\u0027s tokens will be burned.\r\n     * - `from` and `to` are never both zero.\r\n     *\r\n     * To learn more about hooks, head to xref:ROOT:extending-contracts.adoc#using-hooks[Using Hooks].\r\n     */\r\n    function _beforeTokenTransfer(address from, address to, uint256 amount) internal virtual { }\r\n}"},"IERC20.sol":{"content":"// SPDX-License-Identifier: MIT\r\n\r\npragma solidity \u003e=0.6.0 \u003c0.8.0;\r\n\r\n/**\r\n * @dev Interface of the ERC20 standard as defined in the EIP.\r\n */\r\ninterface IERC20 {\r\n    /**\r\n     * @dev Returns the amount of tokens in existence.\r\n     */\r\n    function totalSupply() external view returns (uint256);\r\n\r\n    /**\r\n     * @dev Returns the amount of tokens owned by `account`.\r\n     */\r\n    function balanceOf(address account) external view returns (uint256);\r\n\r\n    /**\r\n     * @dev Moves `amount` tokens from the caller\u0027s account to `recipient`.\r\n     *\r\n     * Returns a boolean value indicating whether the operation succeeded.\r\n     *\r\n     * Emits a {Transfer} event.\r\n     */\r\n    function transfer(address recipient, uint256 amount) external returns (bool);\r\n\r\n    /**\r\n     * @dev Returns the remaining number of tokens that `spender` will be\r\n     * allowed to spend on behalf of `owner` through {transferFrom}. This is\r\n     * zero by default.\r\n     *\r\n     * This value changes when {approve} or {transferFrom} are called.\r\n     */\r\n    function allowance(address owner, address spender) external view returns (uint256);\r\n\r\n    /**\r\n     * @dev Sets `amount` as the allowance of `spender` over the caller\u0027s tokens.\r\n     *\r\n     * Returns a boolean value indicating whether the operation succeeded.\r\n     *\r\n     * IMPORTANT: Beware that changing an allowance with this method brings the risk\r\n     * that someone may use both the old and the new allowance by unfortunate\r\n     * transaction ordering. One possible solution to mitigate this race\r\n     * condition is to first reduce the spender\u0027s allowance to 0 and set the\r\n     * desired value afterwards:\r\n     * https://github.com/ethereum/EIPs/issues/20#issuecomment-263524729\r\n     *\r\n     * Emits an {Approval} event.\r\n     */\r\n    function approve(address spender, uint256 amount) external returns (bool);\r\n\r\n    /**\r\n     * @dev Moves `amount` tokens from `sender` to `recipient` using the\r\n     * allowance mechanism. `amount` is then deducted from the caller\u0027s\r\n     * allowance.\r\n     *\r\n     * Returns a boolean value indicating whether the operation succeeded.\r\n     *\r\n     * Emits a {Transfer} event.\r\n     */\r\n    function transferFrom(address sender, address recipient, uint256 amount) external returns (bool);\r\n\r\n    /**\r\n     * @dev Emitted when `value` tokens are moved from one account (`from`) to\r\n     * another (`to`).\r\n     *\r\n     * Note that `value` may be zero.\r\n     */\r\n    event Transfer(address indexed from, address indexed to, uint256 value);\r\n\r\n    /**\r\n     * @dev Emitted when the allowance of a `spender` for an `owner` is set by\r\n     * a call to {approve}. `value` is the new allowance.\r\n     */\r\n    event Approval(address indexed owner, address indexed spender, uint256 value);\r\n}"},"SafeMath.sol":{"content":"// SPDX-License-Identifier: MIT\r\n\r\npragma solidity \u003e=0.6.0 \u003c0.8.0;\r\n\r\n/**\r\n * @dev Wrappers over Solidity\u0027s arithmetic operations with added overflow\r\n * checks.\r\n *\r\n * Arithmetic operations in Solidity wrap on overflow. This can easily result\r\n * in bugs, because programmers usually assume that an overflow raises an\r\n * error, which is the standard behavior in high level programming languages.\r\n * `SafeMath` restores this intuition by reverting the transaction when an\r\n * operation overflows.\r\n *\r\n * Using this library instead of the unchecked operations eliminates an entire\r\n * class of bugs, so it\u0027s recommended to use it always.\r\n */\r\nlibrary SafeMath {\r\n    /**\r\n     * @dev Returns the addition of two unsigned integers, reverting on\r\n     * overflow.\r\n     *\r\n     * Counterpart to Solidity\u0027s `+` operator.\r\n     *\r\n     * Requirements:\r\n     *\r\n     * - Addition cannot overflow.\r\n     */\r\n    function add(uint256 a, uint256 b) internal pure returns (uint256) {\r\n        uint256 c = a + b;\r\n        require(c \u003e= a, \"SafeMath: addition overflow\");\r\n\r\n        return c;\r\n    }\r\n\r\n    /**\r\n     * @dev Returns the subtraction of two unsigned integers, reverting on\r\n     * overflow (when the result is negative).\r\n     *\r\n     * Counterpart to Solidity\u0027s `-` operator.\r\n     *\r\n     * Requirements:\r\n     *\r\n     * - Subtraction cannot overflow.\r\n     */\r\n    function sub(uint256 a, uint256 b) internal pure returns (uint256) {\r\n        return sub(a, b, \"SafeMath: subtraction overflow\");\r\n    }\r\n\r\n    /**\r\n     * @dev Returns the subtraction of two unsigned integers, reverting with custom message on\r\n     * overflow (when the result is negative).\r\n     *\r\n     * Counterpart to Solidity\u0027s `-` operator.\r\n     *\r\n     * Requirements:\r\n     *\r\n     * - Subtraction cannot overflow.\r\n     */\r\n    function sub(uint256 a, uint256 b, string memory errorMessage) internal pure returns (uint256) {\r\n        require(b \u003c= a, errorMessage);\r\n        uint256 c = a - b;\r\n\r\n        return c;\r\n    }\r\n\r\n    /**\r\n     * @dev Returns the multiplication of two unsigned integers, reverting on\r\n     * overflow.\r\n     *\r\n     * Counterpart to Solidity\u0027s `*` operator.\r\n     *\r\n     * Requirements:\r\n     *\r\n     * - Multiplication cannot overflow.\r\n     */\r\n    function mul(uint256 a, uint256 b) internal pure returns (uint256) {\r\n        // Gas optimization: this is cheaper than requiring \u0027a\u0027 not being zero, but the\r\n        // benefit is lost if \u0027b\u0027 is also tested.\r\n        // See: https://github.com/OpenZeppelin/openzeppelin-contracts/pull/522\r\n        if (a == 0) {\r\n            return 0;\r\n        }\r\n\r\n        uint256 c = a * b;\r\n        require(c / a == b, \"SafeMath: multiplication overflow\");\r\n\r\n        return c;\r\n    }\r\n\r\n    /**\r\n     * @dev Returns the integer division of two unsigned integers. Reverts on\r\n     * division by zero. The result is rounded towards zero.\r\n     *\r\n     * Counterpart to Solidity\u0027s `/` operator. Note: this function uses a\r\n     * `revert` opcode (which leaves remaining gas untouched) while Solidity\r\n     * uses an invalid opcode to revert (consuming all remaining gas).\r\n     *\r\n     * Requirements:\r\n     *\r\n     * - The divisor cannot be zero.\r\n     */\r\n    function div(uint256 a, uint256 b) internal pure returns (uint256) {\r\n        return div(a, b, \"SafeMath: division by zero\");\r\n    }\r\n\r\n    /**\r\n     * @dev Returns the integer division of two unsigned integers. Reverts with custom message on\r\n     * division by zero. The result is rounded towards zero.\r\n     *\r\n     * Counterpart to Solidity\u0027s `/` operator. Note: this function uses a\r\n     * `revert` opcode (which leaves remaining gas untouched) while Solidity\r\n     * uses an invalid opcode to revert (consuming all remaining gas).\r\n     *\r\n     * Requirements:\r\n     *\r\n     * - The divisor cannot be zero.\r\n     */\r\n    function div(uint256 a, uint256 b, string memory errorMessage) internal pure returns (uint256) {\r\n        require(b \u003e 0, errorMessage);\r\n        uint256 c = a / b;\r\n        // assert(a == b * c + a % b); // There is no case in which this doesn\u0027t hold\r\n\r\n        return c;\r\n    }\r\n\r\n    /**\r\n     * @dev Returns the remainder of dividing two unsigned integers. (unsigned integer modulo),\r\n     * Reverts when dividing by zero.\r\n     *\r\n     * Counterpart to Solidity\u0027s `%` operator. This function uses a `revert`\r\n     * opcode (which leaves remaining gas untouched) while Solidity uses an\r\n     * invalid opcode to revert (consuming all remaining gas).\r\n     *\r\n     * Requirements:\r\n     *\r\n     * - The divisor cannot be zero.\r\n     */\r\n    function mod(uint256 a, uint256 b) internal pure returns (uint256) {\r\n        return mod(a, b, \"SafeMath: modulo by zero\");\r\n    }\r\n\r\n    /**\r\n     * @dev Returns the remainder of dividing two unsigned integers. (unsigned integer modulo),\r\n     * Reverts with custom message when dividing by zero.\r\n     *\r\n     * Counterpart to Solidity\u0027s `%` operator. This function uses a `revert`\r\n     * opcode (which leaves remaining gas untouched) while Solidity uses an\r\n     * invalid opcode to revert (consuming all remaining gas).\r\n     *\r\n     * Requirements:\r\n     *\r\n     * - The divisor cannot be zero.\r\n     */\r\n    function mod(uint256 a, uint256 b, string memory errorMessage) internal pure returns (uint256) {\r\n        require(b != 0, errorMessage);\r\n        return a % b;\r\n    }\r\n}"}}