// Contract: Loot
// Target function: function _mint(address to, uint256 tokenId) internal virtual
 is an externally-owned account (EOA) and not a contract.
        *
        * Among others, `isContract` will return false for the following
            * types of addresses:
        *
        *  - an externally-owned account
        *  - a contract in construction
        *  - an address where a contract will be created
        *  - an address where a contract lived, but was destroyed
        * ====
        */
        function isContract(address account) internal view returns (bool) {
                                                                          // This method relies on extcodesize, which returns 0 for contracts in
        // construction, since the code is only stored at the end of the
        // constructor execution.

        uint256 size;
        assembly {
        size := extcodesize(account)
        }
        return size > 0;
        }

        /**
        * @dev Replacement for Solidity's `transfer`: sends `amount` wei to
                                       * `recipient`, forwarding all available gas and reverting on errors.
        *
        * https://eips.ethereum.org/EIPS/eip-1884[EIP1884] increases the gas cost
                                                                             * of certain opcodes, possibly making contracts go over the 2300 gas limit
                                                                                                                                                  * imposed by `transfer`, making them unable to receive funds via
                                                                                                                                                                                                               * `transfer`. {sendValue} removes this limitation.
                                                                                                                                                                                                                                                      *
                                                                                                                                                                                                                                                      * https://diligence.consensys.net/posts/2019/09/stop-using-soliditys-transfer-now/[Learn more].
                                                                                                                                                                                                                                                                                                    *
                                                                                                                                                                                                                                                                                                    * IMPORTANT: because control is transferred to `recipient`, care must be
                                                                                                                                                                                                                                                                                                                                                                          * taken to not create reentrancy vulnerabilities. Consider using
                                                                                                                                                                                                                                                                                                                                                                                                                                     * {ReentrancyGuard} or the
                                                                                                                                                                                                                                                                                                                                                                                                                                     * https://solidity.readthedocs.io/en/v0.5.11/security-considerations.html#use-the-checks-effects-interactions-pattern[checks-effects-interactions pattern].
                                                                                                                                                                                                                                                                                                                                                                                                                                                                              */
                                                                                                                                                                                                                                                                                                                                                                                                                                                                              function sendValue(address payable recipient, uint256 amount) internal {
        require(address(this).balance >= amount, "Address: insufficient balance");

        (bool success, ) = recipient.call{value: amount}("");
        require(success, "Address: unable to send value, recipient may have reverted");
        }

        /**
        * @dev Performs a Solidity function call using a low level `call`. A
                                                                   * plain `call` is an unsafe replacement for a function call: use this
                                                                                                                                    * function instead.
                                                                                                                                               *
                                                                                                                                               * If `target` reverts with a revert reason, it is bubbled up by this
        * function (like regular Solidity function calls).
        *
        * Returns the raw returned data. To convert to the expected return value,
        * use https://solidity.readthedocs.io/en/latest/units-and-global-variables.html?highlight=abi.decode#abi-encoding-and-decoding-functions[`abi.decode`].
        *
        * Requirements:
        *
        * - `target` must be a contract.
        * - calling `target` with `data` must not revert.
        *
        * _Available since v3.1._
        */
        function functionCall(address target, bytes memory data) internal returns (bytes memory) {
        return functionCall(target, data, "Address: low-level call failed");
        }

        /**
        * @dev Same as {xref-Address-functionCall-address-bytes-}[`functionCall`], but with
        * `errorMessage` as a fallback revert reason when `target` reverts.
        *
        * _Available since v3.1._
        */
        function functionCall(
        address target,
        bytes memory data,
        string memory errorMessage
        ) internal returns (bytes memory) {
        return functionCallWithValue(target, data, 0, errorMessage);
        }

        /**
        * @dev Same as {xref-Address-functionCall-address-bytes-}[`functionCall`],
                       * but also transferring `value` wei to `target`.
                                                              *
                                                              * Requirements:
        *
        * - the calling contract must have an ETH balance of at least `value`.
                                                                      * - the called Solidity function must be `payable`.
                                                                                                               *
                                                                                                               * _Available since v3.1._
                                                                                                                                    */
                                                                                                                                    function functionCallWithValue(
        address target,
        bytes memory data,
        uint256 value
        ) internal returns (bytes memory) {
        return functionCallWithValue(target, data, value, "Address: low-level call with value failed");
        }

        /**
        * @dev Same as {xref-Address-functionCallWithValue-address-bytes-uint256-}[`functionCallWithValue`], but
                       * with `errorMessage` as a fallback revert reason when `target` reverts.
        *
        * _Available since v3.1._
        */
        function functionCallWithValue(
        address target,
        bytes memory data,
        uint256 value,
        string memory errorMessage
        ) internal returns (bytes memory) {
        require(address(this).balance >= value, "Address: insufficient balance for call");
        require(isContract(target), "Address: call to non-contract");

        (bool success, bytes memory returndata) = target.call{value: value}(data);
        return _verifyCallResult(success, returndata, errorMessage);
        }

        /**
        * @dev Same as {xref-Address-functionCall-address-bytes-}[`functionCall`],
                       * but performing a static call.
                                                 *
                                                 * _Available since v3.3._
                                                                      */
                                                                      function functionStaticCall(address target, bytes memory data) internal view returns (bytes memory) {
        return functionStaticCall(target, data, "Address: low-level static call failed");
        }

        /**
        * @dev Same as {xref-Address-functionCall-address-bytes-string-}[`functionCall`],
                       * but performing a static call.
                                                 *
                                                 * _Available since v3.3._
                                                                      */
                                                                      function functionStaticCall(
        address target,
        bytes memory data,
        string memory errorMessage
        ) internal view returns (bytes memory) {
        require(isContract(target), "Address: static call to non-contract");

        (bool success, bytes memory returndata) = target.staticcall(data);
        return _verifyCallResult(success, returndata, errorMessage);
        }

        /**
        * @dev Same as {xref-Address-functionCall-address-bytes-}[`functionCall`],
                       * but performing a delegate call.
                                                   *
                                                   * _Available since v3.4._
                                                                        */
                                                                        function functionDelegateCall(address target, bytes memory data) internal returns (bytes memory) {
        return functionDelegateCall(target, data, "Address: low-level delegate call failed");
        }

        /**
        * @dev Same as {xref-Address-functionCall-address-bytes-string-}[`functionCall`],
                       * but performing a delegate call.
                                                   *
                                                   * _Available since v3.4._
                                                                        */
                                                                        function functionDelegateCall(
        address target,
        bytes memory data,
        string memory errorMessage
        ) internal returns (bytes memory) {
        require(isContract(target), "Address: delegate call to non-contract");

        (bool success, bytes memory returndata) = target.delegatecall(data);
        return _verifyCallResult(success, returndata, errorMessage);
        }

        function _verifyCallResult(
        bool success,
        bytes memory returndata,
        string memory errorMessage
        ) private pure returns (bytes memory) {
        if (success) {
        return returndata;
        } else {
        // Look for revert reason and bubble it up if present
        if (returndata.length > 0) {
        // The easiest way to bubble the revert reason is using memory via assembly

        assembly {
        let returndata_size := mload(returndata)
        revert(add(32, returndata), returndata_size)
        }
        } else {
        revert(errorMessage);
        }
        }
        }
        }









        /**
        * @dev Implementation of the {IERC165} interface.
                                               *
                                               * Contracts that want to implement ERC165 should inherit from this contract and override {supportsInterface} to check
                                                                                                                                                               * for the additional interface id that will be supported. For example:
            *
            * ```solidity
                 * function supportsInterface(bytes4 interfaceId) public view virtual override returns (bool) {
            *     return interfaceId == type(MyInterface).interfaceId || super.supportsInterface(interfaceId);
        * }
        * ```
            *
            * Alternatively, {ERC165Storage} provides an easier to use but more expensive implementation.
                                                                                          */
                                                                                          abstract contract ERC165 is IERC165 {
        /**
        * @dev See {IERC165-supportsInterface}.
        */
        function supportsInterface(bytes4 interfaceId) public view virtual override returns (bool) {
        return interfaceId == type(IERC165).interfaceId;
        }
        }


        /**
        * @dev Implementation of https://eips.ethereum.org/EIPS/eip-721[ERC721] Non-Fungible Token Standard, including
                                                                                                   * the Metadata extension, but not including the Enumerable extension, which is available separately as
        * {ERC721Enumerable}.
          */
          contract ERC721 is Context, ERC165, IERC721, IERC721Metadata {
            using Address for address;
        using Strings for uint256;

        // Token name
        string private _name;

        // Token symbol
        string private _symbol;

        // Mapping from token ID to owner address
        mapping(uint256 => address) private _owners;

        // Mapping owner address to token count
        mapping(address => uint256) private _balances;

        // Mapping from token ID to approved address
        mapping(uint256 => address) private _tokenApprovals;

        // Mapping from owner to operator approvals
        mapping(address => mapping(address => bool)) private _operatorApprovals;

        /**
        * @dev Initializes the contract by setting a `name` and a `symbol` to the token collection.
        */
        constructor(string memory name_, string memory symbol_) {
        _name = name_;
        _symbol = symbol_;
        }

        /**
        * @dev See {IERC165-supportsInterface}.
                   */
                   function supportsInterface(bytes4 interfaceId) public view virtual override(ERC165, IERC165) returns (bool) {
        return
        interfaceId == type(IERC721).interfaceId ||
        interfaceId == type(IERC721Metadata).interfaceId ||
        super.supportsInterface(interfaceId);
        }

        /**
        * @dev See {IERC721-balanceOf}.
                   */
                   function balanceOf(address owner) public view virtual override returns (uint256) {
        require(owner != address(0), "ERC721: balance query for the zero address");
        return _balances[owner];
        }

        /**
        * @dev See {IERC721-ownerOf}.
                   */
                   function ownerOf(uint256 tokenId) public view virtual override returns (address) {
        address owner = _owners[tokenId];
        require(owner != address(0), "ERC721: owner query for nonexistent token");
        return owner;
        }

        /**
        * @dev See {IERC721Metadata-name}.
                   */
                   function name() public view virtual override returns (string memory) {
        return _name;
        }

        /**
        * @dev See {IERC721Metadata-symbol}.
                   */
                   function symbol() public view virtual override returns (string memory) {
        return _symbol;
        }

        /**
        * @dev See {IERC721Metadata-tokenURI}.
                   */
                   function tokenURI(uint256 tokenId) public view virtual override returns (string memory) {
        require(_exists(tokenId), "ERC721Metadata: URI query for nonexistent token");

        string memory baseURI = _baseURI();
        return bytes(baseURI).length > 0 ? string(abi.encodePacked(baseURI, tokenId.toString())) : "";
        }

        /**
        * @dev Base URI for computing {tokenURI}. If set, the resulting URI for each
        * token will be the concatenation of the `baseURI` and the `tokenId`. Empty
        * by default, can be overriden in child contracts.
        */
        function _baseURI() internal view virtual returns (string memory) {
        return "";
        }

        /**
        * @dev See {IERC721-approve}.
                   */
                   function approve(address to, uint256 tokenId) public virtual override {
        address owner = ERC721.ownerOf(tokenId);
        require(to != owner, "ERC721: approval to current owner");

        require(
            _msgSender() == owner || isApprovedForAll(owner, _msgSender()),
            "ERC721: approve caller is not owner nor approved for all"
        );

        _approve(to, tokenId);
        }

        /**
        * @dev See {IERC721-getApproved}.
                   */
                   function getApproved(uint256 tokenId) public view virtual override returns (address) {
        require(_exists(tokenId), "ERC721: approved query for nonexistent token");

        return _tokenApprovals[tokenId];
        }

        /**
        * @dev See {IERC721-setApprovalForAll}.
                   */
                   function setApprovalForAll(address operator, bool approved) public virtual override {
        require(operator != _msgSender(), "ERC721: approve to caller");

        _operatorApprovals[_msgSender()][operator] = approved;
        emit ApprovalForAll(_msgSender(), operator, approved);
        }

        /**
        * @dev See {IERC721-isApprovedForAll}.
                   */
                   function isApprovedForAll(address owner, address operator) public view virtual override returns (bool) {
        return _operatorApprovals[owner][operator];
        }

        /**
        * @dev See {IERC721-transferFrom}.
                   */
                   function transferFrom(
        address from,
        address to,
        uint256 tokenId
        ) public virtual override {
        //solhint-disable-next-line max-line-length
        require(_isApprovedOrOwner(_msgSender(), tokenId), "ERC721: transfer caller is not owner nor approved");

        _transfer(from, to, tokenId);
        }

        /**
        * @dev See {IERC721-safeTransferFrom}.
                   */
                   function safeTransferFrom(
        address from,
        address to,
        uint256 tokenId
        ) public virtual override {
        safeTransferFrom(from, to, tokenId, "");
        }

        /**
        * @dev See {IERC721-safeTransferFrom}.
                   */
                   function safeTransferFrom(
        address from,
        address to,
        uint256 tokenId,
        bytes memory _data
        ) public virtual override {
        require(_isApprovedOrOwner(_msgSender(), tokenId), "ERC721: transfer caller is not owner nor approved");
        _safeTransfer(from, to, tokenId, _data);
        }

        /**
        * @dev Safely transfers `tokenId` token from `from` to `to`, checking first that contract recipients
                                                                                                  * are aware of the ERC721 protocol to prevent tokens from being forever locked.
                                                                                                                                                                          *
                                                                                                                                                                          * `_data` is additional data, it has no specified format and it is sent in call to `to`.
                                                                                                                                                                                                                                                             *
                                                                                                                                                                                                                                                             * This internal function is equivalent to {safeTransferFrom}, and can be used to e.g.
                                                                                                                                                                                                                                                                                                                                              * implement alternative mechanisms to perform token transfer, such as signature-based.
                                                                                                                                                                                                                                                                                                                                                                                                                    *
                                                                                                                                                                                                                                                                                                                                                                                                                    * Requirements:
        *
        * - `from` cannot be the zero address.
                                      * - `to` cannot be the zero address.
                                                                  * - `tokenId` token must exist and be owned by `from`.
                                                                                                                      * - If `to` refers to a smart contract, it must implement {IERC721Receiver-onERC721Received}, which is called upon a safe transfer.
                                                                                                                                                                                                                                                *
                                                                                                                                                                                                                                                * Emits a {Transfer} event.
                                                                                                                                                                                                                                                                     */
                                                                                                                                                                                                                                                                     function _safeTransfer(
        address from,
        address to,
        uint256 tokenId,
        bytes memory _data
        ) internal virtual {
        _transfer(from, to, tokenId);
        require(_checkOnERC721Received(from, to, tokenId, _data), "ERC721: transfer to non ERC721Receiver implementer");
        }

        /**
        * @dev Returns whether `tokenId` exists.
                                         *
                                         * Tokens can be managed by their owner or approved accounts via {approve} or {setApprovalForAll}.
                                                                                                         *
                                                                                                         * Tokens start existing when they are minted (`_mint`),
        * and stop existing when they are burned (`_burn`).
                                          */
                                          function _exists(uint256 tokenId) internal view virtual returns (bool) {
        return _owners[tokenId] != address(0);
        }

        /**
        * @dev Returns whether `spender` is allowed to manage `tokenId`.
                                                              *
                                                              * Requirements:
        *
        * - `tokenId` must exist.
                           */
                           function _isApprovedOrOwner(address spender, uint256 tokenId) internal view virtual returns (bool) {
        require(_exists(tokenId), "ERC721: operator query for nonexistent token");
        address owner = ERC721.ownerOf(tokenId);
        return (spender == owner || getApproved(tokenId) == spender || isApprovedForAll(owner, spender));
        }

        /**
        * @dev Safely mints `tokenId` and transfers it to `to`.
                                                          *
                                                          * Requirements:
        *
        * - `tokenId` must not exist.
                               * - If `to` refers to a smart contract, it must implement {IERC721Receiver-onERC721Received}, which is called upon a safe transfer.
                                                                                                                                                         *
                                                                                                                                                         * Emits a {Transfer} event.
                                                                                                                                                                              */
                                                                                                                                                                              function _safeMint(address to, uint256 tokenId) internal virtual {
        _safeMint(to, tokenId, "");
        }

        /**
        * @dev Same as {xref-ERC721-_safeMint-address-uint256-}[`_safeMint`], with an additional `data` parameter which is
        * forwarded in {IERC721Receiver-onERC721Received} to contract recipients.
        */
        function _safeMint(
        address to,
        uint256 tokenId,
        bytes memory _data
        ) internal virtual {
        _mint(to, tokenId);
        require(
            _checkOnERC721Received(address(0), to, tokenId, _data),
            "ERC721: transfer to non ERC721Receiver implementer"
        );
        }