pragma solidity ^0.5.0;


/**
 * @dev Standard math utilities missing in the Solidity language.
 */
library Math {
    /**
     * @dev Returns the largest of two numbers.
     */
    function max(uint256 a, uint256 b) internal pure returns (uint256) {
        return a >= b ? a : b;
    }

    /**
     * @dev Returns the smallest of two numbers.
     */
    function min(uint256 a, uint256 b) internal pure returns (uint256) {
        return a < b ? a : b;
    }

    /**
     * @dev Returns the average of two numbers. The result is rounded towards
     * zero.
     */
    function average(uint256 a, uint256 b) internal pure returns (uint256) {
        // (a + b) / 2 can overflow, so we distribute
        return (a / 2) + (b / 2) + ((a % 2 + b % 2) / 2);
    }
}

/*
 * @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 GSN 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.
 */
contract Context {
    // Empty internal constructor, to prevent people from mistakenly deploying
    // an instance of this contract, which should be used via inheritance.
    constructor () internal { }
    // solhint-disable-previous-line no-empty-blocks

    function _msgSender() internal view returns (address payable) {
        return msg.sender;
    }

    function _msgData() internal view returns (bytes memory) {
        this; // silence state mutability warning without generating bytecode - see https://github.com/ethereum/solidity/issues/2691
        return msg.data;
    }
}

/**
 * @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.
 *
 * 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.
 */
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 () internal {
        address msgSender = _msgSender();
        _owner = msgSender;
        emit OwnershipTransferred(address(0), msgSender);
    }

    /**
     * @dev Returns the address of the current owner.
     */
    function owner() public view returns (address) {
        return _owner;
    }

    /**
     * @dev Throws if called by any account other than the owner.
     */
    modifier onlyOwner() {
        require(isOwner(), "Ownable: caller is not the owner");
        _;
    }

    /**
     * @dev Returns true if the caller is the current owner.
     */
    function isOwner() public view returns (bool) {
        return _msgSender() == _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 onlyOwner {
        emit OwnershipTransferred(_owner, address(0));
        _owner = 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 onlyOwner {
        _transferOwnership(newOwner);
    }

    /**
     * @dev Transfers ownership of the contract to a new account (`newOwner`).
     */
    function _transferOwnership(address newOwner) internal {
        require(newOwner != address(0), "Ownable: new owner is the zero address");
        emit OwnershipTransferred(_owner, newOwner);
        _owner = newOwner;
    }
}

/**
 * @dev Interface of the ERC20 standard as defined in the EIP. Does not include
 * the optional functions; to access them see {ERC20Detailed}.
 */
interface IERC20 {
    /**
     * @dev Returns the amount of tokens in existence.
     */
    function totalSupply() external view returns (uint256);

    /**
     * @dev Returns the amount of tokens owned by `account`.
     */
    function balanceOf(address account) external view returns (uint256);

    /**
     * @dev Moves `amount` tokens from the caller's account to `recipient`.
     *
     * Returns a boolean value indicating whether the operation succeeded.
     *
     * Emits a {Transfer} event.
     */
    function transfer(address recipient, uint256 amount) external returns (bool);

    /**
     * @dev Returns the remaining number of tokens that `spender` will be
     * allowed to spend on behalf of `owner` through {transferFrom}. This is
     * zero by default.
     *
     * This value changes when {approve} or {transferFrom} are called.
     */
    function allowance(address owner, address spender) external view returns (uint256);

    /**
     * @dev Sets `amount` as the allowance of `spender` over the caller's tokens.
     *
     * Returns a boolean value indicating whether the operation succeeded.
     *
     * IMPORTANT: Beware that changing an allowance with this method brings the risk
     * that someone may use both the old and the new allowance by unfortunate
     * transaction ordering. One possible solution to mitigate this race
     * condition is to first reduce the spender's allowance to 0 and set the
     * desired value afterwards:
     * https://github.com/ethereum/EIPs/issues/20#issuecomment-263524729
     *
     * Emits an {Approval} event.
     */
    function approve(address spender, uint256 amount) external returns (bool);

    /**
     * @dev Moves `amount` tokens from `sender` to `recipient` using the
     * allowance mechanism. `amount` is then deducted from the caller's
     * allowance.
     *
     * Returns a boolean value indicating whether the operation succeeded.
     *
     * Emits a {Transfer} event.
     */
    function transferFrom(address sender, address recipient, uint256 amount) external returns (bool);

    /**
     * @dev Emitted when `value` tokens are moved from one account (`from`) to
     * another (`to`).
     *
     * Note that `value` may be zero.
     */
    event Transfer(address indexed from, address indexed to, uint256 value);

    /**
     * @dev Emitted when the allowance of a `spender` for an `owner` is set by
     * a call to {approve}. `value` is the new allowance.
     */
    event Approval(address indexed owner, address indexed spender, uint256 value);
}

/**
 * @title Roles
 * @dev Library for managing addresses assigned to a Role.
 */
library Roles {
    struct Role {
        mapping (address => bool) bearer;
    }

    /**
     * @dev Give an account access to this role.
     */
    function add(Role storage role, address account) internal {
        require(!has(role, account), "Roles: account already has role");
        role.bearer[account] = true;
    }

    /**
     * @dev Remove an account's access to this role.
     */
    function remove(Role storage role, address account) internal {
        require(has(role, account), "Roles: account does not have role");
        role.bearer[account] = false;
    }

    /**
     * @dev Check if an account has this role.
     * @return bool
     */
    function has(Role storage role, address account) internal view returns (bool) {
        require(account != address(0), "Roles: account is the zero address");
        return role.bearer[account];
    }
}

contract MinterRole is Context {
    using Roles for Roles.Role;

    event MinterAdded(address indexed account);
    event MinterRemoved(address indexed account);

    Roles.Role private _minters;

    constructor () internal {
        _addMinter(_msgSender());
    }

    modifier onlyMinter() {
        require(isMinter(_msgSender()), "MinterRole: caller does not have the Minter role");
        _;
    }

    function isMinter(address account) public view returns (bool) {
        return _minters.has(account);
    }

    function addMinter(address account) public onlyMinter {
        _addMinter(account);
    }

    function renounceMinter() public {
        _removeMinter(_msgSender());
    }

    function _addMinter(address account) internal {
        _minters.add(account);
        emit MinterAdded(account);
    }

    function _removeMinter(address account) internal {
        _minters.remove(account);
        emit MinterRemoved(account);
    }
}

/**
 * @title WhitelistAdminRole
 * @dev WhitelistAdmins are responsible for assigning and removing Whitelisted accounts.
 */
contract WhitelistAdminRole is Context {
    using Roles for Roles.Role;

    event WhitelistAdminAdded(address indexed account);
    event WhitelistAdminRemoved(address indexed account);

    Roles.Role private _whitelistAdmins;

    constructor () internal {
        _addWhitelistAdmin(_msgSender());
    }

    modifier onlyWhitelistAdmin() {
        require(isWhitelistAdmin(_msgSender()), "WhitelistAdminRole: caller does not have the WhitelistAdmin role");
        _;
    }

    function isWhitelistAdmin(address account) public view returns (bool) {
        return _whitelistAdmins.has(account);
    }

    function addWhitelistAdmin(address account) public onlyWhitelistAdmin {
        _addWhitelistAdmin(account);
    }

    function renounceWhitelistAdmin() public {
        _removeWhitelistAdmin(_msgSender());
    }

    function _addWhitelistAdmin(address account) internal {
        _whitelistAdmins.add(account);
        emit WhitelistAdminAdded(account);
    }

    function _removeWhitelistAdmin(address account) internal {
        _whitelistAdmins.remove(account);
        emit WhitelistAdminRemoved(account);
    }
}

/**
 * @title ERC165
 * @dev https://github.com/ethereum/EIPs/blob/master/EIPS/eip-165.md
 */
interface IERC165 {

    /**
     * @notice Query if a contract implements an interface
     * @dev Interface identification is specified in ERC-165. This function
     * uses less than 30,000 gas
     * @param _interfaceId The interface identifier, as specified in ERC-165
     */
    function supportsInterface(bytes4 _interfaceId)
    external
    view
    returns (bool);
}

/**
 * @title SafeMath
 * @dev Unsigned math operations with safety checks that revert on error
 */
library SafeMath {

  /**
   * @dev Multiplies two unsigned integers, reverts on overflow.
   */
  function mul(uint256 a, uint256 b) internal pure returns (uint256) {
    // Gas optimization: this is cheaper than requiring 'a' not being zero, but the
    // benefit is lost if 'b' is also tested.
    // See: https://github.com/OpenZeppelin/openzeppelin-solidity/pull/522
    if (a == 0) {
      return 0;
    }

    uint256 c = a * b;
    require(c / a == b, "SafeMath#mul: OVERFLOW");

    return c;
  }

  /**
   * @dev Integer division of two unsigned integers truncating the quotient, reverts on division by zero.
   */
  function div(uint256 a, uint256 b) internal pure returns (uint256) {
    // Solidity only automatically asserts when dividing by 0
    require(b > 0, "SafeMath#div: DIVISION_BY_ZERO");
    uint256 c = a / b;
    // assert(a == b * c + a % b); // There is no case in which this doesn't hold

    return c;
  }

  /**
   * @dev Subtracts two unsigned integers, reverts on overflow (i.e. if subtrahend is greater than minuend).
   */
  function sub(uint256 a, uint256 b) internal pure returns (uint256) {
    require(b <= a, "SafeMath#sub: UNDERFLOW");
    uint256 c = a - b;

    return c;
  }

  /**
   * @dev Adds two unsigned integers, reverts on overflow.
   */
  function add(uint256 a, uint256 b) internal pure returns (uint256) {
    uint256 c = a + b;
    require(c >= a, "SafeMath#add: OVERFLOW");

    return c; 
  }

  /**
   * @dev Divides two unsigned integers and returns the remainder (unsigned integer modulo),
   * reverts when dividing by zero.
   */
  function mod(uint256 a, uint256 b) internal pure returns (uint256) {
    require(b != 0, "SafeMath#mod: DIVISION_BY_ZERO");
    return a % b;
  }

}

/**
 * @dev ERC-1155 interface for accepting safe transfers.
 */
interface IERC1155TokenReceiver {

  /**
   * @notice Handle the receipt of a single ERC1155 token type
   * @dev An ERC1155-compliant smart contract MUST call this function on the token recipient contract, at the end of a `safeTransferFrom` after the balance has been updated
   * This function MAY throw to revert and reject the transfer
   * Return of other amount than the magic value MUST result in the transaction being reverted
   * Note: The token contract address is always the message sender
   * @param _operator  The address which called the `safeTransferFrom` function
   * @param _from      The address which previously owned the token
   * @param _id        The id of the token being transferred
   * @param _amount    The amount of tokens being transferred
   * @param _data      Additional data with no specified format
   * @return           `bytes4(keccak256("onERC1155Received(address,address,uint256,uint256,bytes)"))`
   */
  function onERC1155Received(address _operator, address _from, uint256 _id, uint256 _amount, bytes calldata _data) external returns(bytes4);

  /**
   * @notice Handle the receipt of multiple ERC1155 token types
   * @dev An ERC1155-compliant smart contract MUST call this function on the token recipient contract, at the end of a `safeBatchTransferFrom` after the balances have been updated
   * This function MAY throw to revert and reject the transfer
   * Return of other amount than the magic value WILL result in the transaction being reverted
   * Note: The token contract address is always the message sender
   * @param _operator  The address which called the `safeBatchTransferFrom` function
   * @param _from      The address which previously owned the token
   * @param _ids       An array containing ids of each token being transferred
   * @param _amounts   An array containing amounts of each token being transferred
   * @param _data      Additional data with no specified format
   * @return           `bytes4(keccak256("onERC1155BatchReceived(address,address,uint256[],uint256[],bytes)"))`
   */
  function onERC1155BatchReceived(address _operator, address _from, uint256[] calldata _ids, uint256[] calldata _amounts, bytes calldata _data) external returns(bytes4);

  /**
   * @notice Indicates whether a contract implements the `ERC1155TokenReceiver` functions and so can accept ERC1155 token types.
   * @param  interfaceID The ERC-165 interface ID that is queried for support.s
   * @dev This function MUST return true if it implements the ERC1155TokenReceiver interface and ERC-165 interface.
   *      This function MUST NOT consume more than 5,000 gas.
   * @return Wheter ERC-165 or ERC1155TokenReceiver interfaces are supported.
   */
  function supportsInterface(bytes4 interfaceID) external view returns (bool);

}

interface IERC1155 {
  // Events

  /**
   * @dev Either TransferSingle or TransferBatch MUST emit when tokens are transferred, including zero amount transfers as well as minting or burning
   *   Operator MUST be msg.sender
   *   When minting/creating tokens, the `_from` field MUST be set to `0x0`
   *   When burning/destroying tokens, the `_to` field MUST be set to `0x0`
   *   The total amount transferred from address 0x0 minus the total amount transferred to 0x0 may be used by clients and exchanges to be added to the "circulating supply" for a given token ID
   *   To broadcast the existence of a token ID with no initial balance, the contract SHOULD emit the TransferSingle event from `0x0` to `0x0`, with the token creator as `_operator`, and a `_amount` of 0
   */
  event TransferSingle(address indexed _operator, address indexed _from, address indexed _to, uint256 _id, uint256 _amount);

  /**
   * @dev Either TransferSingle or TransferBatch MUST emit when tokens are transferred, including zero amount transfers as well as minting or burning
   *   Operator MUST be msg.sender
   *   When minting/creating tokens, the `_from` field MUST be set to `0x0`
   *   When burning/destroying tokens, the `_to` field MUST be set to `0x0`
   *   The total amount transferred from address 0x0 minus the total amount transferred to 0x0 may be used by clients and exchanges to be added to the "circulating supply" for a given token ID
   *   To broadcast the existence of multiple token IDs with no initial balance, this SHOULD emit the TransferBatch event from `0x0` to `0x0`, with the token creator as `_operator`, and a `_amount` of 0
   */
  event TransferBatch(address indexed _operator, address indexed _from, address indexed _to, uint256[] _ids, uint256[] _amounts);

  /**
   * @dev MUST emit when an approval is updated
   */
  event ApprovalForAll(address indexed _owner, address indexed _operator, bool _approved);

  /**
   * @dev MUST emit when the URI is updated for a token ID
   *   URIs are defined in RFC 3986
   *   The URI MUST point a JSON file that conforms to the "ERC-1155 Metadata JSON Schema"
   */
  event URI(string _amount, uint256 indexed _id);

  /**
   * @notice Transfers amount of an _id from the _from address to the _to address specified
   * @dev MUST emit TransferSingle event on success
   * Caller must be approved to manage the _from account's tokens (see isApprovedForAll)
   * MUST throw if `_to` is the zero address
   * MUST throw if balance of sender for token `_id` is lower than the `_amount` sent
   * MUST throw on any other error
   * When transfer is complete, this function MUST check if `_to` is a smart contract (code size > 0). If so, it MUST call `onERC1155Received` on `_to` and revert if the return amount is not `bytes4(keccak256("onERC1155Received(address,address,uint256,uint256,bytes)"))`
   * @param _from    Source address
   * @param _to      Target address
   * @param _id      ID of the token type
   * @param _amount  Transfered amount
   * @param _data    Additional data with no specified format, sent in call to `_to`
   */
  function safeTransferFrom(address _from, address _to, uint256 _id, uint256 _amount, bytes calldata _data) external;

  /**
   * @notice Send multiple types of Tokens from the _from address to the _to address (with safety call)
   * @dev MUST emit TransferBatch event on success
   * Caller must be approved to manage the _from account's tokens (see isApprovedForAll)
   * MUST throw if `_to` is the zero address
   * MUST throw if length of `_ids` is not the same as length of `_amounts`
   * MUST throw if any of the balance of sender for token `_ids` is lower than the respective `_amounts` sent
   * MUST throw on any other error
   * When transfer is complete, this function MUST check if `_to` is a smart contract (code size > 0). If so, it MUST call `onERC1155BatchReceived` on `_to` and revert if the return amount is not `bytes4(keccak256("onERC1155BatchReceived(address,address,uint256[],uint256[],bytes)"))`
   * Transfers and events MUST occur in the array order they were submitted (_ids[0] before _ids[1], etc)
   * @param _from     Source addresses
   * @param _to       Target addresses
   * @param _ids      IDs of each token type
   * @param _amounts  Transfer amounts per token type
   * @param _data     Additional data with no specified format, sent in call to `_to`
  */
  function safeBatchTransferFrom(address _from, address _to, uint256[] calldata _ids, uint256[] calldata _amounts, bytes calldata _data) external;
  
  /**
   * @notice Get the balance of an account's Tokens
   * @param _owner  The address of the token holder
   * @param _id     ID of the Token
   * @return        The _owner's balance of the Token type requested
   */
  function balanceOf(address _owner, uint256 _id) external view returns (uint256);

  /**
   * @notice Get the balance of multiple account/token pairs
   * @param _owners The addresses of the token holders
   * @param _ids    ID of the Tokens
   * @return        The _owner's balance of the Token types requested (i.e. balance for each (owner, id) pair)
   */
  function balanceOfBatch(address[] calldata _owners, uint256[] calldata _ids) external view returns (uint256[] memory);

  /**
   * @notice Enable or disable approval for a third party ("operator") to manage all of caller's tokens
   * @dev MUST emit the ApprovalForAll event on success
   * @param _operator  Address to add to the set of authorized operators
   * @param _approved  True if the operator is approved, false to revoke approval
   */
  function setApprovalForAll(address _operator, bool _approved) external;

  /**
   * @notice Queries the approval status of an operator for a given owner
   * @param _owner     The owner of the Tokens
   * @param _operator  Address of authorized operator
   * @return           True if the operator is approved, false if not
   */
  function isApprovedForAll(address _owner, address _operator) external view returns (bool isOperator);

}

/**
 * Copyright 2018 ZeroEx Intl.
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *   http://www.apache.org/licenses/LICENSE-2.0
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
/**
 * Utility library of inline functions on addresses
 */
library Address {

  /**
   * Returns whether the target address is a contract
   * @dev This function will return false if invoked during the constructor of a contract,
   * as the code is not actually created until after the constructor finishes.
   * @param account address of the account to check
   * @return whether the target address is a contract
   */
  function isContract(address account) internal view returns (bool) {
    bytes32 codehash;
    bytes32 accountHash = 0xc5d2460186f7233c927e7db2dcc703c0e500b653ca82273b7bfad8045d85a470;

    // XXX Currently there is no better way to check if there is a contract in an address
    // than to check the size of the code at that address.
    // See https://ethereum.stackexchange.com/a/14016/36603
    // for more details about how this works.
    // TODO Check this again before the Serenity release, because all addresses will be
    // contracts then.
    assembly { codehash := extcodehash(account) }
    return (codehash != 0x0 && codehash != accountHash);
  }

}

/**
 * @dev Implementation of Multi-Token Standard contract
 */
contract ERC1155 is IERC165 {
  using SafeMath for uint256;
  using Address for address;


  /***********************************|
  |        Variables and Events       |
  |__________________________________*/

  // onReceive function signatures
  bytes4 constant internal ERC1155_RECEIVED_VALUE = 0xf23a6e61;
  bytes4 constant internal ERC1155_BATCH_RECEIVED_VALUE = 0xbc197c81;

  // Objects balances
  mapping (address => mapping(uint256 => uint256)) internal balances;

  // Operator Functions
  mapping (address => mapping(address => bool)) internal operators;

  // Events
  event TransferSingle(address indexed _operator, address indexed _from, address indexed _to, uint256 _id, uint256 _amount);
  event TransferBatch(address indexed _operator, address indexed _from, address indexed _to, uint256[] _ids, uint256[] _amounts);
  event ApprovalForAll(address indexed _owner, address indexed _operator, bool _approved);
  event URI(string _uri, uint256 indexed _id);


  /***********************************|
  |     Public Transfer Functions     |
  |__________________________________*/

  /**
   * @notice Transfers amount amount of an _id from the _from address to the _to address specified
   * @param _from    Source address
   * @param _to      Target address
   * @param _id      ID of the token type
   * @param _amount  Transfered amount
   * @param _data    Additional data with no specified format, sent in call to `_to`
   */
  function safeTransferFrom(address _from, address _to, uint256 _id, uint256 _amount, bytes memory _data)
    public
  {
    require((msg.sender == _from) || isApprovedForAll(_from, msg.sender), "ERC1155#safeTransferFrom: INVALID_OPERATOR");
    require(_to != address(0),"ERC1155#safeTransferFrom: INVALID_RECIPIENT");
    // require(_amount >= balances[_from][_id]) is not necessary since checked with safemath operations

    _safeTransferFrom(_from, _to, _id, _amount);
    _callonERC1155Received(_from, _to, _id, _amount, _data);
  }

  /**
   * @notice Send multiple types of Tokens from the _from address to the _to address (with safety call)
   * @param _from     Source addresses
   * @param _to       Target addresses
   * @param _ids      IDs of each token type
   * @param _amounts  Transfer amounts per token type
   * @param _data     Additional data with no specified format, sent in call to `_to`
   */
  function safeBatchTransferFrom(address _from, address _to, uint256[] memory _ids, uint256[] memory _amounts, bytes memory _data)
    public
  {
    // Requirements
    require((msg.sender == _from) || isApprovedForAll(_from, msg.sender), "ERC1155#safeBatchTransferFrom: INVALID_OPERATOR");
    require(_to != address(0), "ERC1155#safeBatchTransferFrom: INVALID_RECIPIENT");

    _safeBatchTransferFrom(_from, _to, _ids, _amounts);
    _callonERC1155BatchReceived(_from, _to, _ids, _amounts, _data);
  }


  /***********************************|
  |    Internal Transfer Functions    |
  |__________________________________*/

  /**
   * @notice Transfers amount amount of an _id from the _from address to the _to address specified
   * @param _from    Source address
   * @param _to      Target address
   * @param _id      ID of the token type
   * @param _amount  Transfered amount
   */
  function _safeTransferFrom(address _from, address _to, uint256 _id, uint256 _amount)
    internal
  {
    // Update balances
    balances[_from][_id] = balances[_from][_id].sub(_amount); // Subtract amount
    balances[_to][_id] = balances[_to][_id].add(_amount);     // Add amount

    // Emit event
    emit TransferSingle(msg.sender, _from, _to, _id, _amount);
  }

  /**
   * @notice Verifies if receiver is contract and if so, calls (_to).onERC1155Received(...)
   */
  function _callonERC1155Received(address _from, address _to, uint256 _id, uint256 _amount, bytes memory _data)
    internal
  {
    // Check if recipient is contract
    if (_to.isContract()) {
      bytes4 retval = IERC1155TokenReceiver(_to).onERC1155Received(msg.sender, _from, _id, _amount, _data);
      require(retval == ERC1155_RECEIVED_VALUE, "ERC1155#_callonERC1155Received: INVALID_ON_RECEIVE_MESSAGE");
    }
  }

  /**
   * @notice Send multiple types of Tokens from the _from address to the _to address (with safety call)
   * @param _from     Source addresses
   * @param _to       Target addresses
   * @param _ids      IDs of each token type
   * @param _amounts  Transfer amounts per token type
   */
  function _safeBatchTransferFrom(address _from, address _to, uint256[] memory _ids, uint256[] memory _amounts)
    internal
  {
    require(_ids.length == _amounts.length, "ERC1155#_safeBatchTransferFrom: INVALID_ARRAYS_LENGTH");

    // Number of transfer to execute
    uint256 nTransfer = _ids.length;

    // Executing all transfers
    for (uint256 i = 0; i < nTransfer; i++) {
      // Update storage balance of previous bin
      balances[_from][_ids[i]] = balances[_from][_ids[i]].sub(_amounts[i]);
      balances[_to][_ids[i]] = balances[_to][_ids[i]].add(_amounts[i]);
    }

    // Emit event
    emit TransferBatch(msg.sender, _from, _to, _ids, _amounts);
  }

  /**
   * @notice Verifies if receiver is contract and if so, calls (_to).onERC1155BatchReceived(...)
   */
  function _callonERC1155BatchReceived(address _from, address _to, uint256[] memory _ids, uint256[] memory _amounts, bytes memory _data)
    internal
  {
    // Pass data if recipient is contract
    if (_to.isContract()) {
      bytes4 retval = IERC1155TokenReceiver(_to).onERC1155BatchReceived(msg.sender, _from, _ids, _amounts, _data);
      require(retval == ERC1155_BATCH_RECEIVED_VALUE, "ERC1155#_callonERC1155BatchReceived: INVALID_ON_RECEIVE_MESSAGE");
    }
  }


  /***********************************|
  |         Operator Functions        |
  |__________________________________*/

  /**
   * @notice Enable or disable approval for a third party ("operator") to manage all of caller's tokens
   * @param _operator  Address to add to the set of authorized operators
   * @param _approved  True if the operator is approved, false to revoke approval
   */
  function setApprovalForAll(address _operator, bool _approved)
    external
  {
    // Update operator status
    operators[msg.sender][_operator] = _approved;
    emit ApprovalForAll(msg.sender, _operator, _approved);
  }

  /**
   * @notice Queries the approval status of an operator for a given owner
   * @param _owner     The owner of the Tokens
   * @param _operator  Address of authorized operator
   * @return True if the operator is approved, false if not
   */
  function isApprovedForAll(address _owner, address _operator)
    public view returns (bool isOperator)
  {
    return operators[_owner][_operator];
  }


  /***********************************|
  |         Balance Functions         |
  |__________________________________*/

  /**
   * @notice Get the balance of an account's Tokens
   * @param _owner  The address of the token holder
   * @param _id     ID of the Token
   * @return The _owner's balance of the Token type requested
   */
  function balanceOf(address _owner, uint256 _id)
    public view returns (uint256)
  {
    return balances[_owner][_id];
  }

  /**
   * @notice Get the balance of multiple account/token pairs
   * @param _owners The addresses of the token holders
   * @param _ids    ID of the Tokens
   * @return        The _owner's balance of the Token types requested (i.e. balance for each (owner, id) pair)
   */
  function balanceOfBatch(address[] memory _owners, uint256[] memory _ids)
    public view returns (uint256[] memory)
  {
    require(_owners.length == _ids.length, "ERC1155#balanceOfBatch: INVALID_ARRAY_LENGTH");

    // Variables
    uint256[] memory batchBalances = new uint256[](_owners.length);

    // Iterate over each owner and token ID
    for (uint256 i = 0; i < _owners.length; i++) {
      batchBalances[i] = balances[_owners[i]][_ids[i]];
    }

    return batchBalances;
  }


  /***********************************|
  |          ERC165 Functions         |
  |__________________________________*/

  /**
   * INTERFACE_SIGNATURE_ERC165 = bytes4(keccak256("supportsInterface(bytes4)"));
   */
  bytes4 constant private INTERFACE_SIGNATURE_ERC165 = 0x01ffc9a7;

  /**
   * INTERFACE_SIGNATURE_ERC1155 =
   * bytes4(keccak256("safeTransferFrom(address,address,uint256,uint256,bytes)")) ^
   * bytes4(keccak256("safeBatchTransferFrom(address,address,uint256[],uint256[],bytes)")) ^
   * bytes4(keccak256("balanceOf(address,uint256)")) ^
   * bytes4(keccak256("balanceOfBatch(address[],uint256[])")) ^
   * bytes4(keccak256("setApprovalForAll(address,bool)")) ^
   * bytes4(keccak256("isApprovedForAll(address,address)"));
   */
  bytes4 constant private INTERFACE_SIGNATURE_ERC1155 = 0xd9b67a26;

  /**
   * @notice Query if a contract implements an interface
   * @param _interfaceID  The interface identifier, as specified in ERC-165
   * @return `true` if the contract implements `_interfaceID` and
   */
  function supportsInterface(bytes4 _interfaceID) external view returns (bool) {
    if (_interfaceID == INTERFACE_SIGNATURE_ERC165 ||
        _interfaceID == INTERFACE_SIGNATURE_ERC1155) {
      return true;
    }
    return false;
  }

}

/**
 * @notice Contract that handles metadata related methods.
 * @dev Methods assume a deterministic generation of URI based on token IDs.
 *      Methods also assume that URI uses hex representation of token IDs.
 */
contract ERC1155Metadata {

  // URI's default URI prefix
  string internal baseMetadataURI;
  event URI(string _uri, uint256 indexed _id);


  /***********************************|
  |     Metadata Public Function s    |
  |__________________________________*/

  /**
   * @notice A distinct Uniform Resource Identifier (URI) for a given token.
   * @dev URIs are defined in RFC 3986.
   *      URIs are assumed to be deterministically generated based on token ID
   *      Token IDs are assumed to be represented in their hex format in URIs
   * @return URI string
   */
  function uri(uint256 _id) public view returns (string memory) {
    return string(abi.encodePacked(baseMetadataURI, _uint2str(_id), ".json"));
  }


  /***********************************|
  |    Metadata Internal Functions    |
  |__________________________________*/

  /**
   * @notice Will emit default URI log event for corresponding token _id
   * @param _tokenIDs Array of IDs of tokens to log default URI
   */
  function _logURIs(uint256[] memory _tokenIDs) internal {
    string memory baseURL = baseMetadataURI;
    string memory tokenURI;

    for (uint256 i = 0; i < _tokenIDs.length; i++) {
      tokenURI = string(abi.encodePacked(baseURL, _uint2str(_tokenIDs[i]), ".json"));
      emit URI(tokenURI, _tokenIDs[i]);
    }
  }

  /**
   * @notice Will emit a specific URI log event for corresponding token
   * @param _tokenIDs IDs of the token corresponding to the _uris logged
   * @param _URIs    The URIs of the specified _tokenIDs
   */
  function _logURIs(uint256[] memory _tokenIDs, string[] memory _URIs) internal {
    require(_tokenIDs.length == _URIs.length, "ERC1155Metadata#_logURIs: INVALID_ARRAYS_LENGTH");
    for (uint256 i = 0; i < _tokenIDs.length; i++) {
      emit URI(_URIs[i], _tokenIDs[i]);
    }
  }

  /**
   * @notice Will update the base URL of token's URI
   * @param _newBaseMetadataURI New base URL of token's URI
   */
  function _setBaseMetadataURI(string memory _newBaseMetadataURI) internal {
    baseMetadataURI = _newBaseMetadataURI;
  }


  /***********************************|
  |    Utility Internal Functions     |
  |__________________________________*/

  /**
   * @notice Convert uint256 to string
   * @param _i Unsigned integer to convert to string
   */
  function _uint2str(uint256 _i) internal pure returns (string memory _uintAsString) {
    if (_i == 0) {
      return "0";
    }

    uint256 j = _i;
    uint256 ii = _i;
    uint256 len;

    // Get number of bytes
    while (j != 0) {
      len++;
      j /= 10;
    }

    bytes memory bstr = new bytes(len);
    uint256 k = len - 1;

    // Get each individual ASCII
    while (ii != 0) {
      bstr[k--] = byte(uint8(48 + ii % 10));
      ii /= 10;
    }

    // Convert to string
    return string(bstr);
  }

}

/**
 * @dev Multi-Fungible Tokens with minting and burning methods. These methods assume
 *      a parent contract to be executed as they are `internal` functions
 */
contract ERC1155MintBurn is ERC1155 {


  /****************************************|
  |            Minting Functions           |
  |_______________________________________*/

  /**
   * @notice Mint _amount of tokens of a given id
   * @param _to      The address to mint tokens to
   * @param _id      Token id to mint
   * @param _amount  The amount to be minted
   * @param _data    Data to pass if receiver is contract
   */
  function _mint(address _to, uint256 _id, uint256 _amount, bytes memory _data)
    internal
  {
    // Add _amount
    balances[_to][_id] = balances[_to][_id].add(_amount);

    // Emit event
    emit TransferSingle(msg.sender, address(0x0), _to, _id, _amount);

    // Calling onReceive method if recipient is contract
    _callonERC1155Received(address(0x0), _to, _id, _amount, _data);
  }

  /**
   * @notice Mint tokens for each ids in _ids
   * @param _to       The address to mint tokens to
   * @param _ids      Array of ids to mint
   * @param _amounts  Array of amount of tokens to mint per id
   * @param _data    Data to pass if receiver is contract
   */
  function _batchMint(address _to, uint256[] memory _ids, uint256[] memory _amounts, bytes memory _data)
    internal
  {
    require(_ids.length == _amounts.length, "ERC1155MintBurn#batchMint: INVALID_ARRAYS_LENGTH");

    // Number of mints to execute
    uint256 nMint = _ids.length;

     // Executing all minting
    for (uint256 i = 0; i < nMint; i++) {
      // Update storage balance
      balances[_to][_ids[i]] = balances[_to][_ids[i]].add(_amounts[i]);
    }

    // Emit batch mint event
    emit TransferBatch(msg.sender, address(0x0), _to, _ids, _amounts);

    // Calling onReceive method if recipient is contract
    _callonERC1155BatchReceived(address(0x0), _to, _ids, _amounts, _data);
  }


  /****************************************|
  |            Burning Functions           |
  |_______________________________________*/

  /**
   * @notice Burn _amount of tokens of a given token id
   * @param _from    The address to burn tokens from
   * @param _id      Token id to burn
   * @param _amount  The amount to be burned
   */
  function _burn(address _from, uint256 _id, uint256 _amount)
    internal
  {
    //Substract _amount
    balances[_from][_id] = balances[_from][_id].sub(_amount);

    // Emit event
    emit TransferSingle(msg.sender, _from, address(0x0), _id, _amount);
  }

  /**
   * @notice Burn tokens of given token id for each (_ids[i], _amounts[i]) pair
   * @param _from     The address to burn tokens from
   * @param _ids      Array of token ids to burn
   * @param _amounts  Array of the amount to be burned
   */
  function _batchBurn(address _from, uint256[] memory _ids, uint256[] memory _amounts)
    internal
  {
    require(_ids.length == _amounts.length, "ERC1155MintBurn#batchBurn: INVALID_ARRAYS_LENGTH");

    // Number of mints to execute
    uint256 nBurn = _ids.length;

     // Executing all minting
    for (uint256 i = 0; i < nBurn; i++) {
      // Update storage balance
      balances[_from][_ids[i]] = balances[_from][_ids[i]].sub(_amounts[i]);
    }

    // Emit batch mint event
    emit TransferBatch(msg.sender, _from, address(0x0), _ids, _amounts);
  }

}

library Strings {
	// via https://github.com/oraclize/ethereum-api/blob/master/oraclizeAPI_0.5.sol
	function strConcat(
		string memory _a,
		string memory _b,
		string memory _c,
		string memory _d,
		string memory _e
	) internal pure returns (string memory) {
		bytes memory _ba = bytes(_a);
		bytes memory _bb = bytes(_b);
		bytes memory _bc = bytes(_c);
		bytes memory _bd = bytes(_d);
		bytes memory _be = bytes(_e);
		string memory abcde = new string(_ba.length + _bb.length + _bc.length + _bd.length + _be.length);
		bytes memory babcde = bytes(abcde);
		uint256 k = 0;
		for (uint256 i = 0; i < _ba.length; i++) babcde[k++] = _ba[i];
		for (uint256 i = 0; i < _bb.length; i++) babcde[k++] = _bb[i];
		for (uint256 i = 0; i < _bc.length; i++) babcde[k++] = _bc[i];
		for (uint256 i = 0; i < _bd.length; i++) babcde[k++] = _bd[i];
		for (uint256 i = 0; i < _be.length; i++) babcde[k++] = _be[i];
		return string(babcde);
	}

	function strConcat(
		string memory _a,
		string memory _b,
		string memory _c,
		string memory _d
	) internal pure returns (string memory) {
		return strConcat(_a, _b, _c, _d, "");
	}

	function strConcat(
		string memory _a,
		string memory _b,
		string memory _c
	) internal pure returns (string memory) {
		return strConcat(_a, _b, _c, "", "");
	}

	function strConcat(string memory _a, string memory _b) internal pure returns (string memory) {
		return strConcat(_a, _b, "", "", "");
	}

	function uint2str(uint256 _i) internal pure returns (string memory _uintAsString) {
		if (_i == 0) {
			return "0";
		}
		uint256 j = _i;
		uint256 len;
		while (j != 0) {
			len++;
			j /= 10;
		}
		bytes memory bstr = new bytes(len);
		uint256 k = len - 1;
		while (_i != 0) {
			bstr[k--] = bytes1(uint8(48 + (_i % 10)));
			_i /= 10;
		}
		return string(bstr);
	}
}

contract OwnableDelegateProxy {}

contract ProxyRegistry {
	mapping(address => OwnableDelegateProxy) public proxies;
}

/**
 * @title ERC1155Tradable
 * ERC1155Tradable - ERC1155 contract that whitelists an operator address, 
 * has create and mint functionality, and supports useful standards from OpenZeppelin,
  like _exists(), name(), symbol(), and totalSupply()
 */
contract ERC1155Tradable is ERC1155, ERC1155MintBurn, ERC1155Metadata, Ownable, MinterRole, WhitelistAdminRole {
	using Strings for string;

	address proxyRegistryAddress;
	uint256 private _currentTokenID = 0;
	mapping(uint256 => address) public creators;
	mapping(uint256 => uint256) public tokenSupply;
	mapping(uint256 => uint256) public tokenMaxSupply;
	// Contract name
	string public name;
	// Contract symbol
	string public symbol;

	constructor(
		string memory _name,
		string memory _symbol,
		address _proxyRegistryAddress
	) public {
		name = _name;
		symbol = _symbol;
		proxyRegistryAddress = _proxyRegistryAddress;
	}

	function removeWhitelistAdmin(address account) public onlyOwner {
		_removeWhitelistAdmin(account);
	}

	function removeMinter(address account) public onlyOwner {
		_removeMinter(account);
	}

	function uri(uint256 _id) public view returns (string memory) {
		require(_exists(_id), "ERC721Tradable#uri: NONEXISTENT_TOKEN");
		return Strings.strConcat(baseMetadataURI, Strings.uint2str(_id));
	}

	/**
	 * @dev Returns the total quantity for a token ID
	 * @param _id uint256 ID of the token to query
	 * @return amount of token in existence
	 */
	function totalSupply(uint256 _id) public view returns (uint256) {
		return tokenSupply[_id];
	}

	/**
	 * @dev Returns the max quantity for a token ID
	 * @param _id uint256 ID of the token to query
	 * @return amount of token in existence
	 */
	function maxSupply(uint256 _id) public view returns (uint256) {
		return tokenMaxSupply[_id];
	}

	/**
	 * @dev Will update the base URL of token's URI
	 * @param _newBaseMetadataURI New base URL of token's URI
	 */
	function setBaseMetadataURI(string memory _newBaseMetadataURI) public onlyWhitelistAdmin {
		_setBaseMetadataURI(_newBaseMetadataURI);
	}

	/**
	 * @dev Creates a new token type and assigns _initialSupply to an address
	 * @param _maxSupply max supply allowed
	 * @param _initialSupply Optional amount to supply the first owner
	 * @param _uri Optional URI for this token type
	 * @param _data Optional data to pass if receiver is contract
	 * @return The newly created token ID
	 */
	function create(
		uint256 _maxSupply,
		uint256 _initialSupply,
		string calldata _uri,
		bytes calldata _data
	) external onlyWhitelistAdmin returns (uint256 tokenId) {
		require(_initialSupply <= _maxSupply, "Initial supply cannot be more than max supply");
		uint256 _id = _getNextTokenID();
		_incrementTokenTypeId();
		creators[_id] = msg.sender;

		if (bytes(_uri).length > 0) {
			emit URI(_uri, _id);
		}

		if (_initialSupply != 0) _mint(msg.sender, _id, _initialSupply, _data);
		tokenSupply[_id] = _initialSupply;
		tokenMaxSupply[_id] = _maxSupply;
		return _id;
	}

	/**
	 * @dev Mints some amount of tokens to an address
	 * @param _to          Address of the future owner of the token
	 * @param _id          Token ID to mint
	 * @param _quantity    Amount of tokens to mint
	 * @param _data        Data to pass if receiver is contract
	 */
	function mint(
		address _to,
		uint256 _id,
		uint256 _quantity,
		bytes memory _data
	) public onlyMinter {
		uint256 tokenId = _id;
		require(tokenSupply[tokenId] < tokenMaxSupply[tokenId], "Max supply reached");
		_mint(_to, _id, _quantity, _data);
		tokenSupply[_id] = tokenSupply[_id].add(_quantity);
	}

	/**
	 * Override isApprovedForAll to whitelist user's OpenSea proxy accounts to enable gas-free listings.
	 */
	function isApprovedForAll(address _owner, address _operator) public view returns (bool isOperator) {
		// Whitelist OpenSea proxy contract for easy trading.
		ProxyRegistry proxyRegistry = ProxyRegistry(proxyRegistryAddress);
		if (address(proxyRegistry.proxies(_owner)) == _operator) {
			return true;
		}

		return ERC1155.isApprovedForAll(_owner, _operator);
	}

	/**
	 * @dev Returns whether the specified token exists by checking to see if it has a creator
	 * @param _id uint256 ID of the token to query the existence of
	 * @return bool whether the token exists
	 */
	function _exists(uint256 _id) internal view returns (bool) {
		return creators[_id] != address(0);
	}

	/**
	 * @dev calculates the next token ID based on value of _currentTokenID
	 * @return uint256 for the next token ID
	 */
	function _getNextTokenID() private view returns (uint256) {
		return _currentTokenID.add(1);
	}

	/**
	 * @dev increments the value of _currentTokenID
	 */
	function _incrementTokenTypeId() private {
		_currentTokenID++;
	}
}

contract MemeTokenWrapper {
	using SafeMath for uint256;
	IERC20 public meme;

	constructor(IERC20 _memeAddress) public {
		meme = IERC20(_memeAddress);
	}

	uint256 private _totalSupply;
	mapping(address => uint256) private _balances;

	function totalSupply() public view returns (uint256) {
		return _totalSupply;
	}

	function balanceOf(address account) public view returns (uint256) {
		return _balances[account];
	}

	function stake(uint256 amount) public {
		_totalSupply = _totalSupply.add(amount);
		_balances[msg.sender] = _balances[msg.sender].add(amount);
		meme.transferFrom(msg.sender, address(this), amount);
	}

	function withdraw(uint256 amount) public {
		_totalSupply = _totalSupply.sub(amount);
		_balances[msg.sender] = _balances[msg.sender].sub(amount);
		meme.transfer(msg.sender, amount);
	}
}

contract GenesisPool is MemeTokenWrapper, Ownable {
	ERC1155Tradable public memes;

	mapping(address => uint256) public lastUpdateTime;
	mapping(address => uint256) public points;
	mapping(uint256 => uint256) public cards;

	event CardAdded(uint256 card, uint256 points);
	event Staked(address indexed user, uint256 amount);
	event Withdrawn(address indexed user, uint256 amount);
	event Redeemed(address indexed user, uint256 amount);

	modifier updateReward(address account) {
		if (account != address(0)) {
			points[account] = earned(account);
			lastUpdateTime[account] = block.timestamp;
		}
		_;
	}

	constructor(ERC1155Tradable _memesAddress, IERC20 _memeAddress) public MemeTokenWrapper(_memeAddress) {
		memes = _memesAddress;
	}

	function addCard(uint256 cardId, uint256 amount) public onlyOwner {
		cards[cardId] = amount;
		emit CardAdded(cardId, amount);
	}

	function earned(address account) public view returns (uint256) {
		uint256 blockTime = block.timestamp;
		return
			points[account].add(
				blockTime.sub(lastUpdateTime[account]).mul(1e18).div(86400).mul(balanceOf(account).div(1e8))
			);
	}

	// stake visibility is public as overriding MemeTokenWrapper's stake() function
	function stake(uint256 amount) public updateReward(msg.sender) {
		require(amount.add(balanceOf(msg.sender)) <= 500000000, "Cannot stake more than 5 meme");

		super.stake(amount);
		emit Staked(msg.sender, amount);
	}

	function withdraw(uint256 amount) public updateReward(msg.sender) {
		require(amount > 0, "Cannot withdraw 0");

		super.withdraw(amount);
		emit Withdrawn(msg.sender, amount);
	}

	function exit() external {
		withdraw(balanceOf(msg.sender));
	}

	function redeem(uint256 card) public updateReward(msg.sender) {
		require(cards[card] != 0, "Card not found");
		require(points[msg.sender] >= cards[card], "Not enough points to redeem for card");
		require(memes.totalSupply(card) < memes.maxSupply(card), "Max cards minted");

		points[msg.sender] = points[msg.sender].sub(cards[card]);
		memes.mint(msg.sender, card, 1, "");
		emit Redeemed(msg.sender, cards[card]);
	}
}

contract DogeCash {
    // Public variables of the token
    string public name;
    string public symbol;
    uint8 public decimals = 18;
    // 18 decimals is the strongly suggested default, avoid changing it
    uint256 public totalSupply;

    // This creates an array with all balances
    mapping (address => uint256) public balanceOf;
    mapping (address => mapping (address => uint256)) public allowance;

    // This generates a public event on the blockchain that will notify clients
    event Transfer(address indexed from, address indexed to, uint256 value);

    // This notifies clients about the amount burnt
    event Burn(address indexed from, uint256 value);

    /**
     * Constrctor function
     *
     * Initializes contract with initial supply tokens to the creator of the contract
     */
    function DogeCash(
        uint256 initialSupply,
        string tokenName,
        string tokenSymbol
    ) public {
        totalSupply = initialSupply * 10 ** uint256(decimals);  // Update total supply with the decimal amount
        balanceOf[msg.sender] = totalSupply;                // Give the creator all initial tokens
        name = tokenName;                                   // Set the name for display purposes
        symbol = tokenSymbol;                               // Set the symbol for display purposes
    }

    /**
     * Internal transfer, only can be called by this contract
     */
    function _transfer(address _from, address _to, uint _value) internal {
        // Prevent transfer to 0x0 address. Use burn() instead
        require(_to != 0x0);
        // Check if the sender has enough
        require(balanceOf[_from] >= _value);
        // Check for overflows
        require(balanceOf[_to] + _value > balanceOf[_to]);
        // Save this for an assertion in the future
        uint previousBalances = balanceOf[_from] + balanceOf[_to];
        // Subtract from the sender
        balanceOf[_from] -= _value;
        // Add the same to the recipient
        balanceOf[_to] += _value;
        Transfer(_from, _to, _value);
        // Asserts are used to use static analysis to find bugs in your code. They should never fail
        assert(balanceOf[_from] + balanceOf[_to] == previousBalances);
    }

    /**
     * Transfer tokens
     *
     * Send `_value` tokens to `_to` from your account
     *
     * @param _to The address of the recipient
     * @param _value the amount to send
     */
    function transfer(address _to, uint256 _value) public {
        _transfer(msg.sender, _to, _value);
    }

    /**
     * Transfer tokens from other address
     *
     * Send `_value` tokens to `_to` in behalf of `_from`
     *
     * @param _from The address of the sender
     * @param _to The address of the recipient
     * @param _value the amount to send
     */
    function transferFrom(address _from, address _to, uint256 _value) public returns (bool success) {
        require(_value <= allowance[_from][msg.sender]);     // Check allowance
        allowance[_from][msg.sender] -= _value;
        _transfer(_from, _to, _value);
        return true;
    }


    /**
     * Destroy tokens
     *
     * Remove `_value` tokens from the system irreversibly
     *
     * @param _value the amount of money to burn
     */
    function burn(uint256 _value) public returns (bool success) {
        require(balanceOf[msg.sender] >= _value);   // Check if the sender has enough
        balanceOf[msg.sender] -= _value;            // Subtract from the sender
        totalSupply -= _value;                      // Updates totalSupply
        Burn(msg.sender, _value);
        return true;
    }

    /**
     * Destroy tokens from other account
     *
     * Remove `_value` tokens from the system irreversibly on behalf of `_from`.
     *
     * @param _from the address of the sender
     * @param _value the amount of money to burn
     */
    function burnFrom(address _from, uint256 _value) public returns (bool success) {
        require(balanceOf[_from] >= _value);                // Check if the targeted balance is enough
        require(_value <= allowance[_from][msg.sender]);    // Check allowance
        balanceOf[_from] -= _value;                         // Subtract from the targeted balance
        allowance[_from][msg.sender] -= _value;             // Subtract from the sender's allowance
        totalSupply -= _value;                              // Update totalSupply
        Burn(_from, _value);
        return true;
    }
}