// Contract: Trash
// Target function: function _mint(address to, uint256 tokenId) internal virtual
 from `from`, this function is called.
*
* It must return its Solidity selector to confirm the token transfer.
* If any other value is returned or the interface is not implemented by the recipient, the transfer will be reverted.
*
* The selector can be obtained in Solidity with `IERC721.onERC721Received.selector`.
    */
function onERC721Received(
    address operator,
            address from,
uint256 tokenId,
        bytes calldata data
) external returns (bytes4);
}







/**
* @title ERC-721 Non-Fungible Token Standard, optional metadata extension
                                                                * @dev See https://eips.ethereum.org/EIPS/eip-721
                                                                                   */
                                                                                   interface IERC721Metadata is IERC721 {
/**
* @dev Returns the token collection name.
*/
function name() external view returns (string memory);

/**
* @dev Returns the token collection symbol.
*/
function symbol() external view returns (string memory);

/**
* @dev Returns the Uniform Resource Identifier (URI) for `tokenId` token.
    */
function tokenURI(uint256 tokenId) external view returns (string memory);
}





/**
* @dev Collection of functions related to the address type
                                                      */
                                                      library Address {
/**
* @dev Returns true if `account` is a contract.
*
* [IMPORTANT]
* ====
* It is unsafe to assume that an address for which this function returns
* false is an externally-owned account (EOA) and not a contract.
*
* Among others, `isContract` will return false for the following
    * types of addresses:
*
*  - an externally-owned account
*  - a contract in construction
*  - an address where a contract will be created
*  - an address where a contract lived, but was destroyed
* ====
*/
function isContract(address account) internal view returns (bool) {
                                                                  // This method relies on extcodesize, which returns 0 for contracts in
// construction, since the code is only stored at the end of the
// constructor execution.

uint256 size;
assembly {
size := extcodesize(account)
}
return size > 0;
}

/**
* @dev Replacement for Solidity's `transfer`: sends `amount` wei to
                               * `recipient`, forwarding all available gas and reverting on errors.
*
* https://eips.ethereum.org/EIPS/eip-1884[EIP1884] increases the gas cost
                                                                     * of certain opcodes, possibly making contracts go over the 2300 gas limit
                                                                                                                                          * imposed by `transfer`, making them unable to receive funds via
                                                                                                                                                                                                       * `transfer`. {sendValue} removes this limitation.
                                                                                                                                                                                                                                              *
                                                                                                                                                                                                                                              * https://diligence.consensys.net/posts/2019/09/stop-using-soliditys-transfer-now/[Learn more].
                                                                                                                                                                                                                                                                                            *
                                                                                                                                                                                                                                                                                            * IMPORTANT: because control is transferred to `recipient`, care must be
                                                                                                                                                                                                                                                                                                                                                                  * taken to not create reentrancy vulnerabilities. Consider using
                                                                                                                                                                                                                                                                                                                                                                                                                             * {ReentrancyGuard} or the
                                                                                                                                                                                                                                                                                                                                                                                                                             * https://solidity.readthedocs.io/en/v0.5.11/security-considerations.html#use-the-checks-effects-interactions-pattern[checks-effects-interactions pattern].
                                                                                                                                                                                                                                                                                                                                                                                                                                                                      */
                                                                                                                                                                                                                                                                                                                                                                                                                                                                      function sendValue(address payable recipient, uint256 amount) internal {
require(address(this).balance >= amount, "Address: insufficient balance");

(bool success, ) = recipient.call{value: amount}("");
require(success, "Address: unable to send value, recipient may have reverted");
}

/**
* @dev Performs a Solidity function call using a low level `call`. A
                                                           * plain `call` is an unsafe replacement for a function call: use this
                                                                                                                            * function instead.
                                                                                                                                       *
                                                                                                                                       * If `target` reverts with a revert reason, it is bubbled up by this
* function (like regular Solidity function calls).
*
* Returns the raw returned data. To convert to the expected return value,
* use https://solidity.readthedocs.io/en/latest/units-and-global-variables.html?highlight=abi.decode#abi-encoding-and-decoding-functions[`abi.decode`].
*
* Requirements:
*
* - `target` must be a contract.
* - calling `target` with `data` must not revert.
*
* _Available since v3.1._
*/
function functionCall(address target, bytes memory data) internal returns (bytes memory) {
return functionCall(target, data, "Address: low-level call failed");
}

/**
* @dev Same as {xref-Address-functionCall-address-bytes-}[`functionCall`], but with
* `errorMessage` as a fallback revert reason when `target` reverts.
*
* _Available since v3.1._
*/
function functionCall(
address target,
bytes memory data,
string memory errorMessage
) internal returns (bytes memory) {
return functionCallWithValue(target, data, 0, errorMessage);
}

/**
* @dev Same as {xref-Address-functionCall-address-bytes-}[`functionCall`],
               * but also transferring `value` wei to `target`.
                                                      *
                                                      * Requirements:
*
* - the calling contract must have an ETH balance of at least `value`.
                                                              * - the called Solidity function must be `payable`.
                                                                                                       *
                                                                                                       * _Available since v3.1._
                                                                                                                            */
                                                                                                                            function functionCallWithValue(
address target,
bytes memory data,
uint256 value
) internal returns (bytes memory) {
return functionCallWithValue(target, data, value, "Address: low-level call with value failed");
}

/**
* @dev Same as {xref-Address-functionCallWithValue-address-bytes-uint256-}[`functionCallWithValue`], but
               * with `errorMessage` as a fallback revert reason when `target` reverts.
*
* _Available since v3.1._
*/
function functionCallWithValue(
address target,
bytes memory data,
uint256 value,
string memory errorMessage
) internal returns (bytes memory) {
require(address(this).balance >= value, "Address: insufficient balance for call");
require(isContract(target), "Address: call to non-contract");

(bool success, bytes memory returndata) = target.call{value: value}(data);
return _verifyCallResult(success, returndata, errorMessage);
}

/**
* @dev Same as {xref-Address-functionCall-address-bytes-}[`functionCall`],
               * but performing a static call.
                                         *
                                         * _Available since v3.3._
                                                              */
                                                              function functionStaticCall(address target, bytes memory data) internal view returns (bytes memory) {
return functionStaticCall(target, data, "Address: low-level static call failed");
}

/**
* @dev Same as {xref-Address-functionCall-address-bytes-string-}[`functionCall`],
               * but performing a static call.
                                         *
                                         * _Available since v3.3._
                                                              */
                                                              function functionStaticCall(
address target,
bytes memory data,
string memory errorMessage
) internal view returns (bytes memory) {
require(isContract(target), "Address: static call to non-contract");

(bool success, bytes memory returndata) = target.staticcall(data);
return _verifyCallResult(success, returndata, errorMessage);
}

/**
* @dev Same as {xref-Address-functionCall-address-bytes-}[`functionCall`],
               * but performing a delegate call.
                                           *
                                           * _Available since v3.4._
                                                                */
                                                                function functionDelegateCall(address target, bytes memory data) internal returns (bytes memory) {
return functionDelegateCall(target, data, "Address: low-level delegate call failed");
}

/**
* @dev Same as {xref-Address-functionCall-address-bytes-string-}[`functionCall`],
               * but performing a delegate call.
                                           *
                                           * _Available since v3.4._
                                                                */
                                                                function functionDelegateCall(
address target,
bytes memory data,
string memory errorMessage
) internal returns (bytes memory) {
require(isContract(target), "Address: delegate call to non-contract");

(bool success, bytes memory returndata) = target.delegatecall(data);
return _verifyCallResult(success, returndata, errorMessage);
}

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"
);
}