// Contract: MBMSFY
// Target function: function _transfer(
..159]		`addr`
		// - [160..223] `startTimestamp`
		// - [224]			`burned`
		// - [225]			`nextInitialized`
		mapping(uint256 => uint256) private _packedOwnerships;

		// Mapping owner address to address data.
		//
		// Bits Layout:
		// - [0..63]		`balance`
		// - [64..127]	`numberMinted`
		// - [128..191] `numberBurned`
		// - [192..255] `aux`
		mapping(address => uint256) private _packedAddressData;

		// 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;

		constructor(string memory name_, string memory symbol_) {
				_name = name_;
				_symbol = symbol_;
				_currentIndex = _startTokenId();
		}

		/**
		 * @dev Returns the starting token ID. 
		 * To change the starting token ID, please override this function.
		 */
		function _startTokenId() internal view virtual returns (uint256) {
				return 0;
		}

		/**
		 * @dev Returns the next token ID to be minted.
		 */
		function _nextTokenId() internal view returns (uint256) {
				return _currentIndex;
		}

		/**
		 * @dev Returns the total number of tokens in existence.
		 * Burned tokens will reduce the count. 
		 * To get the total number of tokens minted, please see `_totalMinted`.
		 */
		function totalSupply() public view override returns (uint256) {
				// Counter underflow is impossible as _burnCounter cannot be incremented
				// more than `_currentIndex - _startTokenId()` times.
				unchecked {
						return _currentIndex - _burnCounter - _startTokenId();
				}
		}

		/**
		 * @dev Returns the total amount of tokens minted in the contract.
		 */
		function _totalMinted() internal view returns (uint256) {
				// Counter underflow is impossible as _currentIndex does not decrement,
				// and it is initialized to `_startTokenId()`
				unchecked {
						return _currentIndex - _startTokenId();
				}
		}

		/**
		 * @dev Returns the total number of tokens burned.
		 */
		function _totalBurned() internal view returns (uint256) {
				return _burnCounter;
		}

		/**
		 * @dev See {IERC165-supportsInterface}.
		 */
		function supportsInterface(bytes4 interfaceId) public view virtual override returns (bool) {
				// The interface IDs are constants representing the first 4 bytes of the XOR of
				// all function selectors in the interface. See: https://eips.ethereum.org/EIPS/eip-165
				// e.g. `bytes4(i.functionA.selector ^ i.functionB.selector ^ ...)`
				return
						interfaceId == 0x01ffc9a7 || // ERC165 interface ID for ERC165.
						interfaceId == 0x80ac58cd || // ERC165 interface ID for ERC721.
						interfaceId == 0x5b5e139f; // ERC165 interface ID for ERC721Metadata.
		}

		/**
		 * @dev See {IERC721-balanceOf}.
		 */
		function balanceOf(address owner) public view override returns (uint256) {
				if (owner == address(0)) revert BalanceQueryForZeroAddress();
				return _packedAddressData[owner] & BITMASK_ADDRESS_DATA_ENTRY;
		}

		/**
		 * Returns the number of tokens minted by `owner`.
		 */
		function _numberMinted(address owner) internal view returns (uint256) {
				return (_packedAddressData[owner] >> BITPOS_NUMBER_MINTED) & BITMASK_ADDRESS_DATA_ENTRY;
		}

		/**
		 * Returns the number of tokens burned by or on behalf of `owner`.
		 */
		function _numberBurned(address owner) internal view returns (uint256) {
				return (_packedAddressData[owner] >> BITPOS_NUMBER_BURNED) & BITMASK_ADDRESS_DATA_ENTRY;
		}

		/**
		 * Returns the auxillary data for `owner`. (e.g. number of whitelist mint slots used).
		 */
		function _getAux(address owner) internal view returns (uint64) {
				return uint64(_packedAddressData[owner] >> BITPOS_AUX);
		}

		/**
		 * Sets the auxillary data for `owner`. (e.g. number of whitelist mint slots used).
		 * If there are multiple variables, please pack them into a uint64.
		 */
		function _setAux(address owner, uint64 aux) internal {
				uint256 packed = _packedAddressData[owner];
				uint256 auxCasted;
				assembly { // Cast aux without masking.
						auxCasted := aux
				}
				packed = (packed & BITMASK_AUX_COMPLEMENT) | (auxCasted << BITPOS_AUX);
				_packedAddressData[owner] = packed;
		}

		/**
		 * Returns the packed ownership data of `tokenId`.
		 */
		function _packedOwnershipOf(uint256 tokenId) private view returns (uint256) {
				uint256 curr = tokenId;

				unchecked {
						if (_startTokenId() <= curr)
								if (curr < _currentIndex) {
										uint256 packed = _packedOwnerships[curr];
										// If not burned.
										if (packed & BITMASK_BURNED == 0) {
												// Invariant:
												// There will always be an ownership that has an address and is not burned
												// before an ownership that does not have an address and is not burned.
												// Hence, curr will not underflow.
												//
												// We can directly compare the packed value.
												// If the address is zero, packed is zero.
												while (packed == 0) {
														packed = _packedOwnerships[--curr];
												}
												return packed;
										}
								}
				}
				revert OwnerQueryForNonexistentToken();
		}

		/**
		 * Returns the unpacked `TokenOwnership` struct from `packed`.
		 */
		function _unpackedOwnership(uint256 packed) private pure returns (TokenOwnership memory ownership) {
				ownership.addr = address(uint160(packed));
				ownership.startTimestamp = uint64(packed >> BITPOS_START_TIMESTAMP);
				ownership.burned = packed & BITMASK_BURNED != 0;
		}

		/**
		 * Returns the unpacked `TokenOwnership` struct at `index`.
		 */
		function _ownershipAt(uint256 index) internal view returns (TokenOwnership memory) {
				return _unpackedOwnership(_packedOwnerships[index]);
		}

		/**
		 * @dev Initializes the ownership slot minted at `index` for efficiency purposes.
		 */
		function _initializeOwnershipAt(uint256 index) internal {
				if (_packedOwnerships[index] == 0) {
						_packedOwnerships[index] = _packedOwnershipOf(index);
				}
		}

		/**
		 * Gas spent here starts off proportional to the maximum mint batch size.
		 * It gradually moves to O(1) as tokens get transferred around in the collection over time.
		 */
		function _ownershipOf(uint256 tokenId) internal view returns (TokenOwnership memory) {
				return _unpackedOwnership(_packedOwnershipOf(tokenId));
		}

		/**
		 * @dev See {IERC721-ownerOf}.
		 */
		function ownerOf(uint256 tokenId) public view override returns (address) {
				return address(uint160(_packedOwnershipOf(tokenId)));
		}

		/**
		 * @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) {
				if (!_exists(tokenId)) revert URIQueryForNonexistentToken();

				string memory baseURI = _baseURI();
				return bytes(baseURI).length != 0 ? string(abi.encodePacked(baseURI, _toString(tokenId))) : '';
		}

		/**
		 * @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 Casts the address to uint256 without masking.
		 */
		function _addressToUint256(address value) private pure returns (uint256 result) {
				assembly {
						result := value
				}
		}

		/**
		 * @dev Casts the boolean to uint256 without branching.
		 */
		function _boolToUint256(bool value) private pure returns (uint256 result) {
				assembly {
						result := value
				}
		}

		/**
		 * @dev See {IERC721-approve}.
		 */
		function approve(address to, uint256 tokenId) public override {
				address owner = address(uint160(_packedOwnershipOf(tokenId)));
				if (to == owner) revert ApprovalToCurrentOwner();

				if (_msgSenderERC721A() != owner)
						if (!isApprovedForAll(owner, _msgSenderERC721A())) {
								revert ApprovalCallerNotOwnerNorApproved();
						}

				_tokenApprovals[tokenId] = to;
				emit Approval(owner, to, tokenId);
		}

		/**
		 * @dev See {IERC721-getApproved}.
		 */
		function getApproved(uint256 tokenId) public view override returns (address) {
				if (!_exists(tokenId)) revert ApprovalQueryForNonexistentToken();

				return _tokenApprovals[tokenId];
		}

		/**
		 * @dev See {IERC721-setApprovalForAll}.
		 */
		function setApprovalForAll(address operator, bool approved) public virtual override {
				if (operator == _msgSenderERC721A()) revert ApproveToCaller();

				_operatorApprovals[_msgSenderERC721A()][operator] = approved;
				emit ApprovalForAll(_msgSenderERC721A(), 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 {
				_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 {
				_transfer(from, to, tokenId);
				if (to.code.length != 0)
						if (!_checkContractOnERC721Received(from, to, tokenId, _data)) {
								revert TransferToNonERC721ReceiverImplementer();
						}
		}

		/**
		 * @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`),
		 */
		function _exists(uint256 tokenId) internal view returns (bool) {
				return
						_startTokenId() <= tokenId &&
						tokenId < _currentIndex && // If within bounds,
						_packedOwnerships[tokenId] & BITMASK_BURNED == 0; // and not burned.
		}

		/**
		 * @dev Equivalent to `_safeMint(to, quantity, '')`.
		 */
		function _safeMint(address to, uint256 quantity) internal {
				_safeMint(to, quantity, '');
		}

		/**
		 * @dev Safely mints `quantity` tokens and transfers them to `to`.
		 *
		 * Requirements:
		 *
		 * - If `to` refers to a smart contract, it must implement
		 *	 {IERC721Receiver-onERC721Received}, which is called for each safe transfer.
		 * - `quantity` must be greater than 0.
		 *
		 * Emits a {Transfer} event.
		 */
		function _safeMint(
				address to,
				uint256 quantity,
				bytes memory _data
		) internal {
				uint256 startTokenId = _currentIndex;
				if (to == address(0)) revert MintToZeroAddress();
				if (quantity == 0) revert MintZeroQuantity();

				_beforeTokenTransfers(address(0), to, startTokenId, quantity);

				// Overflows are incredibly unrealistic.
				// balance or numberMinted overflow if current value of either + quantity > 1.8e19 (2**64) - 1
				// updatedIndex overflows if _currentIndex + quantity > 1.2e77 (2**256) - 1
				unchecked {
						// Updates:
						// - `balance += quantity`.
						// - `numberMinted += quantity`.
						//
						// We can directly add to the balance and number minted.
						_packedAddressData[to] += quantity * ((1 << BITPOS_NUMBER_MINTED) | 1);

						// Updates:
						// - `address` to the owner.
						// - `startTimestamp` to the timestamp of minting.
						// - `burned` to `false`.
						// - `nextInitialized` to `quantity == 1`.
						_packedOwnerships[startTokenId] =
								_addressToUint256(to) |
								(block.timestamp << BITPOS_START_TIMESTAMP) |
								(_boolToUint256(quantity == 1) << BITPOS_NEXT_INITIALIZED);

						uint256 updatedIndex = startTokenId;
						uint256 end = updatedIndex + quantity;

						if (to.code.length != 0) {
								do {
										emit Transfer(address(0), to, updatedIndex);
										if (!_checkContractOnERC721Received(address(0), to, updatedIndex++, _data)) {
												revert TransferToNonERC721ReceiverImplementer();
										}
								} while (updatedIndex < end);
								// Reentrancy protection
								if (_currentIndex != startTokenId) revert();
						} else {
								do {
										emit Transfer(address(0), to, updatedIndex++);
								} while (updatedIndex < end);
						}
						_currentIndex = updatedIndex;
				}
				_afterTokenTransfers(address(0), to, startTokenId, quantity);
		}

		/**
		 * @dev Mints `quantity` tokens and transfers them to `to`.
		 *
		 * Requirements:
		 *
		 * - `to` cannot be the zero address.
		 * - `quantity` must be greater than 0.
		 *
		 * Emits a {Transfer} event.
		 */
		function _mint(address to, uint256 quantity) internal {
				uint256 startTokenId = _currentIndex;
				if (to == address(0)) revert MintToZeroAddress();
				if (quantity == 0) revert MintZeroQuantity();

				_beforeTokenTransfers(address(0), to, startTokenId, quantity);

				// Overflows are incredibly unrealistic.
				// balance or numberMinted overflow if current value of either + quantity > 1.8e19 (2**64) - 1
				// updatedIndex overflows if _currentIndex + quantity > 1.2e77 (2**256) - 1
				unchecked {
						// Updates:
						// - `balance += quantity`.
						// - `numberMinted += quantity`.
						//
						// We can directly add to the balance and number minted.
						_packedAddressData[to] += quantity * ((1 << BITPOS_NUMBER_MINTED) | 1);

						// Updates:
						// - `address` to the owner.
						// - `startTimestamp` to the timestamp of minting.
						// - `burned` to `false`.
						// - `nextInitialized` to `quantity == 1`.
						_packedOwnerships[startTokenId] =
								_addressToUint256(to) |
								(block.timestamp << BITPOS_START_TIMESTAMP) |
								(_boolToUint256(quantity == 1) << BITPOS_NEXT_INITIALIZED);

						uint256 updatedIndex = startTokenId;
						uint256 end = updatedIndex + quantity;

						do {
								emit Transfer(address(0), to, updatedIndex++);
						} while (updatedIndex < end);

						_currentIndex = updatedIndex;
				}
				_afterTokenTransfers(address(0), to, startTokenId, quantity);
		}