// SPDX-License-Identifier: MIT
pragma solidity ^0.8.20;

/**
 * @dev Interface of the ERC165 standard, as defined in the
 * https://eips.ethereum.org/EIPS/eip-165[EIP].
 *
 * Implementers can declare support of contract interfaces, which can then be
 * queried by others ({ERC165Checker}).
 *
 * For an implementation, see {ERC165}.
 */
interface IERC165 {
	/**
	 * @dev Returns true if this contract implements the interface defined by
     * `interfaceId`. See the corresponding
     * https://eips.ethereum.org/EIPS/eip-165#how-interfaces-are-identified[EIP section]
     * to learn more about how these ids are created.
     *
     * This function call must use less than 30 000 gas.
     */
	function supportsInterface(bytes4 interfaceId) external view returns (bool);
}

/**
 * @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 String operations.
 */
library Strings {
	bytes16 private constant _HEX_SYMBOLS = "0123456789abcdef";
	uint8 private constant _ADDRESS_LENGTH = 20;
	
	/**
	 * @dev Converts a `uint256` to its ASCII `string` decimal representation.
     */
	function toString(uint256 value) internal pure returns (string memory) {
		// Inspired by OraclizeAPI's implementation - MIT licence
		// https://github.com/oraclize/ethereum-api/blob/b42146b063c7d6ee1358846c198246239e9360e8/oraclizeAPI_0.4.25.sol
		
		if (value == 0) {
			return "0";
		}
		uint256 temp = value;
		uint256 digits;
		while (temp != 0) {
			digits++;
			temp /= 10;
		}
		bytes memory buffer = new bytes(digits);
		while (value != 0) {
			digits -= 1;
			buffer[digits] = bytes1(uint8(48 + uint256(value % 10)));
			value /= 10;
		}
		return string(buffer);
	}
	
	/**
	 * @dev Converts a `uint256` to its ASCII `string` hexadecimal representation.
     */
	function toHexString(uint256 value) internal pure returns (string memory) {
		if (value == 0) {
			return "0x00";
		}
		uint256 temp = value;
		uint256 length = 0;
		while (temp != 0) {
			length++;
			temp >>= 8;
		}
		return toHexString(value, length);
	}
	
	/**
	 * @dev Converts a `uint256` to its ASCII `string` hexadecimal representation with fixed length.
     */
	function toHexString(uint256 value, uint256 length) internal pure returns (string memory) {
		bytes memory buffer = new bytes(2 * length + 2);
		buffer[0] = "0";
		buffer[1] = "x";
		for (uint256 i = 2 * length + 1; i > 1; --i) {
			buffer[i] = _HEX_SYMBOLS[value & 0xf];
			value >>= 4;
		}
		require(value == 0, "Strings: hex length insufficient");
		return string(buffer);
	}
	
	/**
	 * @dev Converts an `address` with fixed length of 20 bytes to its not checksummed ASCII `string` hexadecimal representation.
     */
	function toHexString(address addr) internal pure returns (string memory) {
		return toHexString(uint256(uint160(addr)), _ADDRESS_LENGTH);
	}
}

/**
 * @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 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.
 */
abstract contract Context {
	function _msgSender() internal view virtual returns (address) {
		return msg.sender;
	}
	
	function _msgData() internal view virtual returns (bytes calldata) {
		return msg.data;
	}
}
/**
 * @dev External interface of AccessControl declared to support ERC165 detection.
 */
interface IAccessControl {
	/**
	 * @dev Emitted when `newAdminRole` is set as ``role``'s admin role, replacing `previousAdminRole`
     *
     * `DEFAULT_ADMIN_ROLE` is the starting admin for all roles, despite
     * {RoleAdminChanged} not being emitted signaling this.
     *
     * _Available since v3.1._
     */
	event RoleAdminChanged(bytes32 indexed role, bytes32 indexed previousAdminRole, bytes32 indexed newAdminRole);
	
	/**
	 * @dev Emitted when `account` is granted `role`.
     *
     * `sender` is the account that originated the contract call, an admin role
     * bearer except when using {AccessControl-_setupRole}.
     */
	event RoleGranted(bytes32 indexed role, address indexed account, address indexed sender);
	
	/**
	 * @dev Emitted when `account` is revoked `role`.
     *
     * `sender` is the account that originated the contract call:
     *   - if using `revokeRole`, it is the admin role bearer
     *   - if using `renounceRole`, it is the role bearer (i.e. `account`)
     */
	event RoleRevoked(bytes32 indexed role, address indexed account, address indexed sender);
	
	/**
	 * @dev Returns `true` if `account` has been granted `role`.
     */
	function hasRole(bytes32 role, address account) external view returns (bool);
	
	/**
	 * @dev Returns the admin role that controls `role`. See {grantRole} and
     * {revokeRole}.
     *
     * To change a role's admin, use {AccessControl-_setRoleAdmin}.
     */
	function getRoleAdmin(bytes32 role) external view returns (bytes32);
	
	/**
	 * @dev Grants `role` to `account`.
     *
     * If `account` had not been already granted `role`, emits a {RoleGranted}
     * event.
     *
     * Requirements:
     *
     * - the caller must have ``role``'s admin role.
     */
	function grantRole(bytes32 role, address account) external;
	
	/**
	 * @dev Revokes `role` from `account`.
     *
     * If `account` had been granted `role`, emits a {RoleRevoked} event.
     *
     * Requirements:
     *
     * - the caller must have ``role``'s admin role.
     */
	function revokeRole(bytes32 role, address account) external;
	
	/**
	 * @dev Revokes `role` from the calling account.
     *
     * Roles are often managed via {grantRole} and {revokeRole}: this function's
     * purpose is to provide a mechanism for accounts to lose their privileges
     * if they are compromised (such as when a trusted device is misplaced).
     *
     * If the calling account had been granted `role`, emits a {RoleRevoked}
     * event.
     *
     * Requirements:
     *
     * - the caller must be `account`.
     */
	function renounceRole(bytes32 role, address account) external;
}

/**
 * @dev Contract module that allows children to implement role-based access
 * control mechanisms. This is a lightweight version that doesn't allow enumerating role
 * members except through off-chain means by accessing the contract event logs. Some
 * applications may benefit from on-chain enumerability, for those cases see
 * {AccessControlEnumerable}.
 *
 * Roles are referred to by their `bytes32` identifier. These should be exposed
 * in the external API and be unique. The best way to achieve this is by
 * using `public constant` hash digests:
 *
 * ```
 * bytes32 public constant MY_ROLE = keccak256("MY_ROLE");
 * ```
 *
 * Roles can be used to represent a set of permissions. To restrict access to a
 * function call, use {hasRole}:
 *
 * ```
 * function foo() public {
 *     require(hasRole(MY_ROLE, msg.sender));
 *     ...
 * }
 * ```
 *
 * Roles can be granted and revoked dynamically via the {grantRole} and
 * {revokeRole} functions. Each role has an associated admin role, and only
 * accounts that have a role's admin role can call {grantRole} and {revokeRole}.
 *
 * By default, the admin role for all roles is `DEFAULT_ADMIN_ROLE`, which means
 * that only accounts with this role will be able to grant or revoke other
 * roles. More complex role relationships can be created by using
 * {_setRoleAdmin}.
 *
 * WARNING: The `DEFAULT_ADMIN_ROLE` is also its own admin: it has permission to
 * grant and revoke this role. Extra precautions should be taken to secure
 * accounts that have been granted it.
 */
abstract contract AccessControl is Context, IAccessControl, ERC165 {
	struct RoleData {
		mapping(address => bool) members;
		bytes32 adminRole;
	}
	
	mapping(bytes32 => RoleData) private _roles;
	
	bytes32 public constant DEFAULT_ADMIN_ROLE = 0x00;
	
	/**
	 * @dev Modifier that checks that an account has a specific role. Reverts
     * with a standardized message including the required role.
     *
     * The format of the revert reason is given by the following regular expression:
     *
     *  /^AccessControl: account (0x[0-9a-f]{40}) is missing role (0x[0-9a-f]{64})$/
     *
     * _Available since v4.1._
     */
	modifier onlyRole(bytes32 role) {
		_checkRole(role);
		_;
	}
	
	/**
	 * @dev See {IERC165-supportsInterface}.
     */
	function supportsInterface(bytes4 interfaceId) public view virtual override returns (bool) {
		return interfaceId == type(IAccessControl).interfaceId || super.supportsInterface(interfaceId);
	}
	
	/**
	 * @dev Returns `true` if `account` has been granted `role`.
     */
	function hasRole(bytes32 role, address account) public view virtual override returns (bool) {
		return _roles[role].members[account];
	}
	
	/**
	 * @dev Revert with a standard message if `_msgSender()` is missing `role`.
     * Overriding this function changes the behavior of the {onlyRole} modifier.
     *
     * Format of the revert message is described in {_checkRole}.
     *
     * _Available since v4.6._
     */
	function _checkRole(bytes32 role) internal view virtual {
		_checkRole(role, _msgSender());
	}
	
	/**
	 * @dev Revert with a standard message if `account` is missing `role`.
     *
     * The format of the revert reason is given by the following regular expression:
     *
     *  /^AccessControl: account (0x[0-9a-f]{40}) is missing role (0x[0-9a-f]{64})$/
     */
	function _checkRole(bytes32 role, address account) internal view virtual {
		if (!hasRole(role, account)) {
			revert(
				string(
				abi.encodePacked(
					"AccessControl: account ",
					Strings.toHexString(uint160(account), 20),
					" is missing role ",
					Strings.toHexString(uint256(role), 32)
				)
			)
			);
		}
	}
	
	/**
	 * @dev Returns the admin role that controls `role`. See {grantRole} and
     * {revokeRole}.
     *
     * To change a role's admin, use {_setRoleAdmin}.
     */
	function getRoleAdmin(bytes32 role) public view virtual override returns (bytes32) {
		return _roles[role].adminRole;
	}
	
	/**
	 * @dev Grants `role` to `account`.
     *
     * If `account` had not been already granted `role`, emits a {RoleGranted}
     * event.
     *
     * Requirements:
     *
     * - the caller must have ``role``'s admin role.
     *
     * May emit a {RoleGranted} event.
     */
	function grantRole(bytes32 role, address account) public virtual override onlyRole(getRoleAdmin(role)) {
		_grantRole(role, account);
	}
	
	/**
	 * @dev Revokes `role` from `account`.
     *
     * If `account` had been granted `role`, emits a {RoleRevoked} event.
     *
     * Requirements:
     *
     * - the caller must have ``role``'s admin role.
     *
     * May emit a {RoleRevoked} event.
     */
	function revokeRole(bytes32 role, address account) public virtual override onlyRole(getRoleAdmin(role)) {
		_revokeRole(role, account);
	}
	
	/**
	 * @dev Revokes `role` from the calling account.
     *
     * Roles are often managed via {grantRole} and {revokeRole}: this function's
     * purpose is to provide a mechanism for accounts to lose their privileges
     * if they are compromised (such as when a trusted device is misplaced).
     *
     * If the calling account had been revoked `role`, emits a {RoleRevoked}
     * event.
     *
     * Requirements:
     *
     * - the caller must be `account`.
     *
     * May emit a {RoleRevoked} event.
     */
	function renounceRole(bytes32 role, address account) public virtual override {
		require(account == _msgSender(), "AccessControl: can only renounce roles for self");
		
		_revokeRole(role, account);
	}
	
	/**
	 * @dev Grants `role` to `account`.
     *
     * If `account` had not been already granted `role`, emits a {RoleGranted}
     * event. Note that unlike {grantRole}, this function doesn't perform any
     * checks on the calling account.
     *
     * May emit a {RoleGranted} event.
     *
     * [WARNING]
     * ====
     * This function should only be called from the constructor when setting
     * up the initial roles for the system.
     *
     * Using this function in any other way is effectively circumventing the admin
     * system imposed by {AccessControl}.
     * ====
     *
     * NOTE: This function is deprecated in favor of {_grantRole}.
     */
	function _setupRole(bytes32 role, address account) internal virtual {
		_grantRole(role, account);
	}
	
	/**
	 * @dev Sets `adminRole` as ``role``'s admin role.
     *
     * Emits a {RoleAdminChanged} event.
     */
	function _setRoleAdmin(bytes32 role, bytes32 adminRole) internal virtual {
		bytes32 previousAdminRole = getRoleAdmin(role);
		_roles[role].adminRole = adminRole;
		emit RoleAdminChanged(role, previousAdminRole, adminRole);
	}
	
	/**
	 * @dev Grants `role` to `account`.
     *
     * Internal function without access restriction.
     *
     * May emit a {RoleGranted} event.
     */
	function _grantRole(bytes32 role, address account) internal virtual {
		if (!hasRole(role, account)) {
			_roles[role].members[account] = true;
			emit RoleGranted(role, account, _msgSender());
		}
	}
	
	/**
	 * @dev Revokes `role` from `account`.
     *
     * Internal function without access restriction.
     *
     * May emit a {RoleRevoked} event.
     */
	function _revokeRole(bytes32 role, address account) internal virtual {
		if (hasRole(role, account)) {
			_roles[role].members[account] = false;
			emit RoleRevoked(role, account, _msgSender());
		}
	}
}

/**
 * @dev Interface of ERC721A.
 */
interface IERC721A {
	/**
	 * The caller must own the token or be an approved operator.
	 */
	error ApprovalCallerNotOwnerNorApproved();
	
	/**
	 * The token does not exist.
	 */
	error ApprovalQueryForNonexistentToken();
	
	/**
	 * The caller cannot approve to their own address.
	 */
	error ApproveToCaller();
	
	/**
	 * Cannot query the balance for the zero address.
	 */
	error BalanceQueryForZeroAddress();
	
	/**
	 * Cannot mint to the zero address.
	 */
	error MintToZeroAddress();
	
	/**
	 * The quantity of tokens minted must be more than zero.
	 */
	error MintZeroQuantity();
	
	/**
	 * The token does not exist.
	 */
	error OwnerQueryForNonexistentToken();
	
	/**
	 * The caller must own the token or be an approved operator.
	 */
	error TransferCallerNotOwnerNorApproved();
	
	/**
	 * The token must be owned by `from`.
	 */
	error TransferFromIncorrectOwner();
	
	/**
	 * Cannot safely transfer to a contract that does not implement the
	 * ERC721Receiver interface.
	 */
	error TransferToNonERC721ReceiverImplementer();
	
	/**
	 * Cannot transfer to the zero address.
	 */
	error TransferToZeroAddress();
	
	/**
	 * The token does not exist.
	 */
	error URIQueryForNonexistentToken();
	
	/**
	 * The `quantity` minted with ERC2309 exceeds the safety limit.
	 */
	error MintERC2309QuantityExceedsLimit();
	
	/**
	 * The `extraData` cannot be set on an unintialized ownership slot.
	 */
	error OwnershipNotInitializedForExtraData();
	
	// =============================================================
	//                            STRUCTS
	// =============================================================
	
	struct TokenOwnership {
		// The address of the owner.
		address addr;
		// Stores the start time of ownership with minimal overhead for tokenomics.
		uint64 startTimestamp;
		// Whether the token has been burned.
		bool burned;
		// Arbitrary data similar to `startTimestamp` that can be set via {_extraData}.
		uint24 extraData;
	}
	
	// =============================================================
	//                         TOKEN COUNTERS
	// =============================================================
	
	/**
	 * @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() external view returns (uint256);
	
	// =============================================================
	//                            IERC165
	// =============================================================
	
	/**
	 * @dev Returns true if this contract implements the interface defined by
     * `interfaceId`. See the corresponding
     * [EIP section](https://eips.ethereum.org/EIPS/eip-165#how-interfaces-are-identified)
     * to learn more about how these ids are created.
     *
     * This function call must use less than 30000 gas.
     */
	function supportsInterface(bytes4 interfaceId) external view returns (bool);
	
	// =============================================================
	//                            IERC721
	// =============================================================
	
	/**
	 * @dev Emitted when `tokenId` token is transferred from `from` to `to`.
     */
	event Transfer(address indexed from, address indexed to, uint256 indexed tokenId);
	
	/**
	 * @dev Emitted when `owner` enables `approved` to manage the `tokenId` token.
     */
	event Approval(address indexed owner, address indexed approved, uint256 indexed tokenId);
	
	/**
	 * @dev Emitted when `owner` enables or disables
     * (`approved`) `operator` to manage all of its assets.
     */
	event ApprovalForAll(address indexed owner, address indexed operator, bool approved);
	
	/**
	 * @dev Returns the number of tokens in `owner`'s account.
     */
	function balanceOf(address owner) external view returns (uint256 balance);
	
	/**
	 * @dev Returns the owner of the `tokenId` token.
     *
     * Requirements:
     *
     * - `tokenId` must exist.
     */
	function ownerOf(uint256 tokenId) external view returns (address owner);
	
	/**
	 * @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.
     *
     * Requirements:
     *
     * - `from` cannot be the zero address.
     * - `to` cannot be the zero address.
     * - `tokenId` token must exist and be owned by `from`.
     * - If the caller is not `from`, it must be have been allowed to move
     * this token by either {approve} or {setApprovalForAll}.
     * - If `to` refers to a smart contract, it must implement
     * {IERC721Receiver-onERC721Received}, which is called upon a safe transfer.
     *
     * Emits a {Transfer} event.
     */
	function safeTransferFrom(
		address from,
		address to,
		uint256 tokenId,
		bytes calldata data
	) external;
	
	/**
	 * @dev Equivalent to `safeTransferFrom(from, to, tokenId, '')`.
     */
	function safeTransferFrom(
		address from,
		address to,
		uint256 tokenId
	) external;
	
	/**
	 * @dev Transfers `tokenId` from `from` to `to`.
     *
     * WARNING: Usage of this method is discouraged, use {safeTransferFrom}
     * whenever possible.
     *
     * Requirements:
     *
     * - `from` cannot be the zero address.
     * - `to` cannot be the zero address.
     * - `tokenId` token must be owned by `from`.
     * - If the caller is not `from`, it must be approved to move this token
     * by either {approve} or {setApprovalForAll}.
     *
     * Emits a {Transfer} event.
     */
	function transferFrom(
		address from,
		address to,
		uint256 tokenId
	) external;
	
	/**
	 * @dev Gives permission to `to` to transfer `tokenId` token to another account.
     * The approval is cleared when the token is transferred.
     *
     * Only a single account can be approved at a time, so approving the
     * zero address clears previous approvals.
     *
     * Requirements:
     *
     * - The caller must own the token or be an approved operator.
     * - `tokenId` must exist.
     *
     * Emits an {Approval} event.
     */
	function approve(address to, uint256 tokenId) external;
	
	/**
	 * @dev Approve or remove `operator` as an operator for the caller.
     * Operators can call {transferFrom} or {safeTransferFrom}
     * for any token owned by the caller.
     *
     * Requirements:
     *
     * - The `operator` cannot be the caller.
     *
     * Emits an {ApprovalForAll} event.
     */
	function setApprovalForAll(address operator, bool _approved) external;
	
	/**
	 * @dev Returns the account approved for `tokenId` token.
     *
     * Requirements:
     *
     * - `tokenId` must exist.
     */
	function getApproved(uint256 tokenId) external view returns (address operator);
	
	/**
	 * @dev Returns if the `operator` is allowed to manage all of the assets of `owner`.
     *
     * See {setApprovalForAll}.
     */
	function isApprovedForAll(address owner, address operator) external view returns (bool);
	
	// =============================================================
	//                        IERC721Metadata
	// =============================================================
	
	/**
	 * @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);
	
	// =============================================================
	//                           IERC2309
	// =============================================================
	
	/**
	 * @dev Emitted when tokens in `fromTokenId` to `toTokenId`
     * (inclusive) is transferred from `from` to `to`, as defined in the
     * [ERC2309](https://eips.ethereum.org/EIPS/eip-2309) standard.
     *
     * See {_mintERC2309} for more details.
     */
	event ConsecutiveTransfer(uint256 indexed fromTokenId, uint256 toTokenId, address indexed from, address indexed to);
}
/**
 * @dev Interface of ERC721 token receiver.
 */
interface ERC721A__IERC721Receiver {
	function onERC721Received(
		address operator,
		address from,
		uint256 tokenId,
		bytes calldata data
	) external returns (bytes4);
}

/**
 * @title ERC721A
 *
 * @dev Implementation of the [ERC721](https://eips.ethereum.org/EIPS/eip-721)
 * Non-Fungible Token Standard, including the Metadata extension.
 * Optimized for lower gas during batch mints.
 *
 * Token IDs are minted in sequential order (e.g. 0, 1, 2, 3, ...)
 * starting from `_startTokenId()`.
 *
 * Assumptions:
 *
 * - An owner cannot have more than 2**64 - 1 (max value of uint64) of supply.
 * - The maximum token ID cannot exceed 2**256 - 1 (max value of uint256).
 */
contract ERC721A is IERC721A{
	// Reference type for token approval.
	struct TokenApprovalRef {
		address value;
	}
	
	// =============================================================
	//                           CONSTANTS
	// =============================================================
	
	// Mask of an entry in packed address data.
	uint256 private constant _BITMASK_ADDRESS_DATA_ENTRY = (1 << 64) - 1;
	
	// The bit position of `numberMinted` in packed address data.
	uint256 private constant _BITPOS_NUMBER_MINTED = 64;
	
	// The bit position of `numberBurned` in packed address data.
	uint256 private constant _BITPOS_NUMBER_BURNED = 128;
	
	// The bit position of `aux` in packed address data.
	uint256 private constant _BITPOS_AUX = 192;
	
	// Mask of all 256 bits in packed address data except the 64 bits for `aux`.
	uint256 private constant _BITMASK_AUX_COMPLEMENT = (1 << 192) - 1;
	
	// The bit position of `startTimestamp` in packed ownership.
	uint256 private constant _BITPOS_START_TIMESTAMP = 160;
	
	// The bit mask of the `burned` bit in packed ownership.
	uint256 private constant _BITMASK_BURNED = 1 << 224;
	
	// The bit position of the `nextInitialized` bit in packed ownership.
	uint256 private constant _BITPOS_NEXT_INITIALIZED = 225;
	
	// The bit mask of the `nextInitialized` bit in packed ownership.
	uint256 private constant _BITMASK_NEXT_INITIALIZED = 1 << 225;
	
	// The bit position of `extraData` in packed ownership.
	uint256 private constant _BITPOS_EXTRA_DATA = 232;
	
	// Mask of all 256 bits in a packed ownership except the 24 bits for `extraData`.
	uint256 private constant _BITMASK_EXTRA_DATA_COMPLEMENT = (1 << 232) - 1;
	
	// The mask of the lower 160 bits for addresses.
	uint256 private constant _BITMASK_ADDRESS = (1 << 160) - 1;
	
	// The maximum `quantity` that can be minted with {_mintERC2309}.
	// This limit is to prevent overflows on the address data entries.
	// For a limit of 5000, a total of 3.689e15 calls to {_mintERC2309}
	// is required to cause an overflow, which is unrealistic.
	uint256 private constant _MAX_MINT_ERC2309_QUANTITY_LIMIT = 5000;
	
	// The `Transfer` event signature is given by:
	// `keccak256(bytes("Transfer(address,address,uint256)"))`.
	bytes32 private constant _TRANSFER_EVENT_SIGNATURE =
	0xddf252ad1be2c89b69c2b068fc378daa952ba7f163c4a11628f55a4df523b3ef;
	
	// =============================================================
	//                            STORAGE
	// =============================================================
	
	// The next token ID to be minted.
	uint256 private _currentIndex;
	
	// The number of tokens burned.
	uint256 private _burnCounter;
	
	// Token name
	string private _name;
	
	// Token symbol
	string private _symbol;
	
	// Mapping from token ID to ownership details
	// An empty struct value does not necessarily mean the token is unowned.
	// See {_packedOwnershipOf} implementation for details.
	//
	// Bits Layout:
	// - [0..159]   `addr`
	// - [160..223] `startTimestamp`
	// - [224]      `burned`
	// - [225]      `nextInitialized`
	// - [232..255] `extraData`
	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 => TokenApprovalRef) private _tokenApprovals;
	
	// Mapping from owner to operator approvals
	mapping(address => mapping(address => bool)) private _operatorApprovals;
	
	// =============================================================
	//                          CONSTRUCTOR
	// =============================================================
	
	constructor(string memory name_, string memory symbol_) {
		_name = name_;
		_symbol = symbol_;
		_currentIndex = _startTokenId();
	}
	
	// =============================================================
	//                   TOKEN COUNTING OPERATIONS
	// =============================================================
	
	/**
	 * @dev Returns the starting token ID.
     * To change the starting token ID, please override this function.
     */
	function _startTokenId() internal view virtual returns (uint256) {
		return 1;
	}
	
	/**
	 * @dev Returns the next token ID to be minted.
     */
	function _nextTokenId() internal view virtual 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 virtual 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 virtual 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 virtual returns (uint256) {
		return _burnCounter;
	}
	
	// =============================================================
	//                    ADDRESS DATA OPERATIONS
	// =============================================================
	
	/**
	 * @dev Returns the number of tokens in `owner`'s account.
     */
	function balanceOf(address owner) public view virtual 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 auxiliary 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 auxiliary 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 virtual {
		uint256 packed = _packedAddressData[owner];
		uint256 auxCasted;
		// Cast `aux` with assembly to avoid redundant masking.
		assembly {
			auxCasted := aux
		}
		packed = (packed & _BITMASK_AUX_COMPLEMENT) | (auxCasted << _BITPOS_AUX);
		_packedAddressData[owner] = packed;
	}
	
	// =============================================================
	//                            IERC165
	// =============================================================
	
	/**
	 * @dev Returns true if this contract implements the interface defined by
     * `interfaceId`. See the corresponding
     * [EIP section](https://eips.ethereum.org/EIPS/eip-165#how-interfaces-are-identified)
     * to learn more about how these ids are created.
     *
     * This function call must use less than 30000 gas.
     */
	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: [ERC165](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.
	}
	
	// =============================================================
	//                        IERC721Metadata
	// =============================================================
	
	/**
	 * @dev Returns the token collection name.
     */
	function name() public view virtual override returns (string memory) {
		return _name;
	}
	
	/**
	 * @dev Returns the token collection symbol.
     */
	function symbol() public view virtual override returns (string memory) {
		return _symbol;
	}
	
	/**
	 * @dev Returns the Uniform Resource Identifier (URI) for `tokenId` token.
     */
	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, it can be overridden in child contracts.
     */
	function _baseURI() internal view virtual returns (string memory) {
		return '';
	}
	
	// =============================================================
	//                     OWNERSHIPS OPERATIONS
	// =============================================================
	
	/**
	 * @dev Returns the owner of the `tokenId` token.
     *
     * Requirements:
     *
     * - `tokenId` must exist.
     */
	function ownerOf(uint256 tokenId) public view virtual override returns (address) {
		return address(uint160(_packedOwnershipOf(tokenId)));
	}
	
	/**
	 * @dev Gas spent here starts off proportional to the maximum mint batch size.
     * It gradually moves to O(1) as tokens get transferred around over time.
     */
	function _ownershipOf(uint256 tokenId) internal view virtual returns (TokenOwnership memory) {
		return _unpackedOwnership(_packedOwnershipOf(tokenId));
	}
	
	/**
	 * @dev Returns the unpacked `TokenOwnership` struct at `index`.
     */
	function _ownershipAt(uint256 index) internal view virtual returns (TokenOwnership memory) {
		return _unpackedOwnership(_packedOwnerships[index]);
	}
	
	/**
	 * @dev Initializes the ownership slot minted at `index` for efficiency purposes.
     */
	function _initializeOwnershipAt(uint256 index) internal virtual {
		if (_packedOwnerships[index] == 0) {
			_packedOwnerships[index] = _packedOwnershipOf(index);
		}
	}
	
	/**
	 * 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 initialized ownership slot
						// (i.e. `ownership.addr != address(0) && ownership.burned == false`)
						// before an unintialized ownership slot
						// (i.e. `ownership.addr == address(0) && ownership.burned == false`)
						// Hence, `curr` will not underflow.
						//
						// We can directly compare the packed value.
						// If the address is zero, packed will be zero.
						while (packed == 0) {
							packed = _packedOwnerships[--curr];
						}
						return packed;
					}
				}
		}
		revert OwnerQueryForNonexistentToken();
	}
	
	/**
	 * @dev 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;
		ownership.extraData = uint24(packed >> _BITPOS_EXTRA_DATA);
	}
	
	/**
	 * @dev Packs ownership data into a single uint256.
     */
	function _packOwnershipData(address owner, uint256 flags) private view returns (uint256 result) {
		assembly {
		// Mask `owner` to the lower 160 bits, in case the upper bits somehow aren't clean.
			owner := and(owner, _BITMASK_ADDRESS)
		// `owner | (block.timestamp << _BITPOS_START_TIMESTAMP) | flags`.
			result := or(owner, or(shl(_BITPOS_START_TIMESTAMP, timestamp()), flags))
		}
	}
	
	/**
	 * @dev Returns the `nextInitialized` flag set if `quantity` equals 1.
     */
	function _nextInitializedFlag(uint256 quantity) private pure returns (uint256 result) {
		// For branchless setting of the `nextInitialized` flag.
		assembly {
		// `(quantity == 1) << _BITPOS_NEXT_INITIALIZED`.
			result := shl(_BITPOS_NEXT_INITIALIZED, eq(quantity, 1))
		}
	}
	
	// =============================================================
	//                      APPROVAL OPERATIONS
	// =============================================================
	
	/**
	 * @dev Gives permission to `to` to transfer `tokenId` token to another account.
     * The approval is cleared when the token is transferred.
     *
     * Only a single account can be approved at a time, so approving the
     * zero address clears previous approvals.
     *
     * Requirements:
     *
     * - The caller must own the token or be an approved operator.
     * - `tokenId` must exist.
     *
     * Emits an {Approval} event.
     */
	function approve(address to, uint256 tokenId) public virtual override {
		address owner = ownerOf(tokenId);
		
		if (_msgSenderERC721A() != owner)
			if (!isApprovedForAll(owner, _msgSenderERC721A())) {
				revert ApprovalCallerNotOwnerNorApproved();
			}
		
		_tokenApprovals[tokenId].value = to;
		emit Approval(owner, to, tokenId);
	}
	
	/**
	 * @dev Returns the account approved for `tokenId` token.
     *
     * Requirements:
     *
     * - `tokenId` must exist.
     */
	function getApproved(uint256 tokenId) public view virtual override returns (address) {
		if (!_exists(tokenId)) revert ApprovalQueryForNonexistentToken();
		
		return _tokenApprovals[tokenId].value;
	}
	
	/**
	 * @dev Approve or remove `operator` as an operator for the caller.
     * Operators can call {transferFrom} or {safeTransferFrom}
     * for any token owned by the caller.
     *
     * Requirements:
     *
     * - The `operator` cannot be the caller.
     *
     * Emits an {ApprovalForAll} event.
     */
	function setApprovalForAll(address operator, bool approved) public virtual override {
		if (operator == _msgSenderERC721A()) revert ApproveToCaller();
		
		_operatorApprovals[_msgSenderERC721A()][operator] = approved;
		emit ApprovalForAll(_msgSenderERC721A(), operator, approved);
	}
	
	/**
	 * @dev Returns if the `operator` is allowed to manage all of the assets of `owner`.
     *
     * See {setApprovalForAll}.
     */
	function isApprovedForAll(address owner, address operator) public view virtual override returns (bool) {
		return _operatorApprovals[owner][operator];
	}
	
	/**
	 * @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. See {_mint}.
     */
	function _exists(uint256 tokenId) internal view virtual returns (bool) {
		return
			_startTokenId() <= tokenId &&
			tokenId < _currentIndex && // If within bounds,
			_packedOwnerships[tokenId] & _BITMASK_BURNED == 0; // and not burned.
	}
	
	/**
	 * @dev Returns whether `msgSender` is equal to `approvedAddress` or `owner`.
     */
	function _isSenderApprovedOrOwner(
		address approvedAddress,
		address owner,
		address msgSender
	) private pure returns (bool result) {
		assembly {
		// Mask `owner` to the lower 160 bits, in case the upper bits somehow aren't clean.
			owner := and(owner, _BITMASK_ADDRESS)
		// Mask `msgSender` to the lower 160 bits, in case the upper bits somehow aren't clean.
			msgSender := and(msgSender, _BITMASK_ADDRESS)
		// `msgSender == owner || msgSender == approvedAddress`.
			result := or(eq(msgSender, owner), eq(msgSender, approvedAddress))
		}
	}
	
	/**
	 * @dev Returns the storage slot and value for the approved address of `tokenId`.
     */
	function _getApprovedSlotAndAddress(uint256 tokenId)
	private
	view
	returns (uint256 approvedAddressSlot, address approvedAddress)
	{
		TokenApprovalRef storage tokenApproval = _tokenApprovals[tokenId];
		// The following is equivalent to `approvedAddress = _tokenApprovals[tokenId]`.
		assembly {
			approvedAddressSlot := tokenApproval.slot
			approvedAddress := sload(approvedAddressSlot)
		}
	}
	
	// =============================================================
	//                      TRANSFER OPERATIONS
	// =============================================================
	
	/**
	 * @dev Transfers `tokenId` from `from` to `to`.
     *
     * Requirements:
     *
     * - `from` cannot be the zero address.
     * - `to` cannot be the zero address.
     * - `tokenId` token must be owned by `from`.
     * - If the caller is not `from`, it must be approved to move this token
     * by either {approve} or {setApprovalForAll}.
     *
     * Emits a {Transfer} event.
     */
	function transferFrom(
		address from,
		address to,
		uint256 tokenId
	) public virtual override {
		uint256 prevOwnershipPacked = _packedOwnershipOf(tokenId);
		
		if (address(uint160(prevOwnershipPacked)) != from) revert TransferFromIncorrectOwner();
		
		(uint256 approvedAddressSlot, address approvedAddress) = _getApprovedSlotAndAddress(tokenId);
		
		// The nested ifs save around 20+ gas over a compound boolean condition.
		if (!_isSenderApprovedOrOwner(approvedAddress, from, _msgSenderERC721A()))
			if (!isApprovedForAll(from, _msgSenderERC721A())) revert TransferCallerNotOwnerNorApproved();
		
		if (to == address(0)) revert TransferToZeroAddress();
		
		_beforeTokenTransfers(from, to, tokenId, 1);
		
		// Clear approvals from the previous owner.
		assembly {
			if approvedAddress {
			// This is equivalent to `delete _tokenApprovals[tokenId]`.
				sstore(approvedAddressSlot, 0)
			}
		}
		
		// Underflow of the sender's balance is impossible because we check for
		// ownership above and the recipient's balance can't realistically overflow.
		// Counter overflow is incredibly unrealistic as `tokenId` would have to be 2**256.
		unchecked {
		// We can directly increment and decrement the balances.
			--_packedAddressData[from]; // Updates: `balance -= 1`.
			++_packedAddressData[to]; // Updates: `balance += 1`.
		
		// Updates:
		// - `address` to the next owner.
		// - `startTimestamp` to the timestamp of transfering.
		// - `burned` to `false`.
		// - `nextInitialized` to `true`.
			_packedOwnerships[tokenId] = _packOwnershipData(
				to,
				_BITMASK_NEXT_INITIALIZED | _nextExtraData(from, to, prevOwnershipPacked)
			);
		
		// If the next slot may not have been initialized (i.e. `nextInitialized == false`) .
			if (prevOwnershipPacked & _BITMASK_NEXT_INITIALIZED == 0) {
				uint256 nextTokenId = tokenId + 1;
				// If the next slot's address is zero and not burned (i.e. packed value is zero).
				if (_packedOwnerships[nextTokenId] == 0) {
					// If the next slot is within bounds.
					if (nextTokenId != _currentIndex) {
						// Initialize the next slot to maintain correctness for `ownerOf(tokenId + 1)`.
						_packedOwnerships[nextTokenId] = prevOwnershipPacked;
					}
				}
			}
		}
		
		emit Transfer(from, to, tokenId);
		_afterTokenTransfers(from, to, tokenId, 1);
	}
	
	/**
	 * @dev Equivalent to `safeTransferFrom(from, to, tokenId, '')`.
     */
	function safeTransferFrom(
		address from,
		address to,
		uint256 tokenId
	) public virtual override {
		safeTransferFrom(from, to, tokenId, '');
	}
	
	/**
	 * @dev Safely transfers `tokenId` token from `from` to `to`.
     *
     * Requirements:
     *
     * - `from` cannot be the zero address.
     * - `to` cannot be the zero address.
     * - `tokenId` token must exist and be owned by `from`.
     * - If the caller is not `from`, it must be approved to move this token
     * by either {approve} or {setApprovalForAll}.
     * - If `to` refers to a smart contract, it must implement
     * {IERC721Receiver-onERC721Received}, which is called upon a safe transfer.
     *
     * Emits a {Transfer} event.
     */
	function safeTransferFrom(
		address from,
		address to,
		uint256 tokenId,
		bytes memory _data
	) public virtual override {
		transferFrom(from, to, tokenId);
		if (to.code.length != 0)
			if (!_checkContractOnERC721Received(from, to, tokenId, _data)) {
				revert TransferToNonERC721ReceiverImplementer();
			}
	}
	
	/**
	 * @dev Hook that is called before a set of serially-ordered token IDs
     * are about to be transferred. This includes minting.
     * And also called before burning one token.
     *
     * `startTokenId` - the first token ID to be transferred.
     * `quantity` - the amount to be transferred.
     *
     * Calling conditions:
     *
     * - When `from` and `to` are both non-zero, `from`'s `tokenId` will be
     * transferred to `to`.
     * - When `from` is zero, `tokenId` will be minted for `to`.
     * - When `to` is zero, `tokenId` will be burned by `from`.
     * - `from` and `to` are never both zero.
     */
	function _beforeTokenTransfers(
		address from,
		address to,
		uint256 startTokenId,
		uint256 quantity
	) internal virtual {}
	
	/**
	 * @dev Hook that is called after a set of serially-ordered token IDs
     * have been transferred. This includes minting.
     * And also called after one token has been burned.
     *
     * `startTokenId` - the first token ID to be transferred.
     * `quantity` - the amount to be transferred.
     *
     * Calling conditions:
     *
     * - When `from` and `to` are both non-zero, `from`'s `tokenId` has been
     * transferred to `to`.
     * - When `from` is zero, `tokenId` has been minted for `to`.
     * - When `to` is zero, `tokenId` has been burned by `from`.
     * - `from` and `to` are never both zero.
     */
	function _afterTokenTransfers(
		address from,
		address to,
		uint256 startTokenId,
		uint256 quantity
	) internal virtual {}
	
	/**
	 * @dev Private function to invoke {IERC721Receiver-onERC721Received} on a target contract.
     *
     * `from` - Previous owner of the given token ID.
     * `to` - Target address that will receive the token.
     * `tokenId` - Token ID to be transferred.
     * `_data` - Optional data to send along with the call.
     *
     * Returns whether the call correctly returned the expected magic value.
     */
	function _checkContractOnERC721Received(
		address from,
		address to,
		uint256 tokenId,
		bytes memory _data
	) private returns (bool) {
		try ERC721A__IERC721Receiver(to).onERC721Received(_msgSenderERC721A(), from, tokenId, _data) returns (
			bytes4 retval
		) {
			return retval == ERC721A__IERC721Receiver(to).onERC721Received.selector;
		} catch (bytes memory reason) {
			if (reason.length == 0) {
				revert TransferToNonERC721ReceiverImplementer();
			} else {
				assembly {
					revert(add(32, reason), mload(reason))
				}
			}
		}
	}
	
	// =============================================================
	//                        MINT OPERATIONS
	// =============================================================
	
	/**
	 * @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 for each mint.
     */
	function _mint(address to, uint256 quantity) internal virtual {
		uint256 startTokenId = _currentIndex;
		if (quantity == 0) revert MintZeroQuantity();
		
		_beforeTokenTransfers(address(0), to, startTokenId, quantity);
		
		// Overflows are incredibly unrealistic.
		// `balance` and `numberMinted` have a maximum limit of 2**64.
		// `tokenId` has a maximum limit of 2**256.
		unchecked {
		// Updates:
		// - `balance += quantity`.
		// - `numberMinted += quantity`.
		//
		// We can directly add to the `balance` and `numberMinted`.
			_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] = _packOwnershipData(
				to,
				_nextInitializedFlag(quantity) | _nextExtraData(address(0), to, 0)
			);
			
			uint256 toMasked;
			uint256 end = startTokenId + quantity;
		
		// Use assembly to loop and emit the `Transfer` event for gas savings.
			assembly {
			// Mask `to` to the lower 160 bits, in case the upper bits somehow aren't clean.
				toMasked := and(to, _BITMASK_ADDRESS)
			// Emit the `Transfer` event.
				log4(
					0, // Start of data (0, since no data).
					0, // End of data (0, since no data).
					_TRANSFER_EVENT_SIGNATURE, // Signature.
					0, // `address(0)`.
					toMasked, // `to`.
					startTokenId // `tokenId`.
				)
				
				for {
					let tokenId := add(startTokenId, 1)
				} iszero(eq(tokenId, end)) {
					tokenId := add(tokenId, 1)
				} {
				// Emit the `Transfer` event. Similar to above.
					log4(0, 0, _TRANSFER_EVENT_SIGNATURE, 0, toMasked, tokenId)
				}
			}
			if (toMasked == 0) revert MintToZeroAddress();
			
			_currentIndex = end;
		}
		_afterTokenTransfers(address(0), to, startTokenId, quantity);
	}
	
	/**
	 * @dev Mints `quantity` tokens and transfers them to `to`.
     *
     * This function is intended for efficient minting only during contract creation.
     *
     * It emits only one {ConsecutiveTransfer} as defined in
     * [ERC2309](https://eips.ethereum.org/EIPS/eip-2309),
     * instead of a sequence of {Transfer} event(s).
     *
     * Calling this function outside of contract creation WILL make your contract
     * non-compliant with the ERC721 standard.
     * For full ERC721 compliance, substituting ERC721 {Transfer} event(s) with the ERC2309
     * {ConsecutiveTransfer} event is only permissible during contract creation.
     *
     * Requirements:
     *
     * - `to` cannot be the zero address.
     * - `quantity` must be greater than 0.
     *
     * Emits a {ConsecutiveTransfer} event.
     */
	function _mintERC2309(address to, uint256 quantity) internal virtual {
		uint256 startTokenId = _currentIndex;
		if (to == address(0)) revert MintToZeroAddress();
		if (quantity == 0) revert MintZeroQuantity();
		if (quantity > _MAX_MINT_ERC2309_QUANTITY_LIMIT) revert MintERC2309QuantityExceedsLimit();
		
		_beforeTokenTransfers(address(0), to, startTokenId, quantity);
		
		// Overflows are unrealistic due to the above check for `quantity` to be below the limit.
		unchecked {
		// Updates:
		// - `balance += quantity`.
		// - `numberMinted += quantity`.
		//
		// We can directly add to the `balance` and `numberMinted`.
			_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] = _packOwnershipData(
				to,
				_nextInitializedFlag(quantity) | _nextExtraData(address(0), to, 0)
			);
			
			emit ConsecutiveTransfer(startTokenId, startTokenId + quantity - 1, address(0), to);
			
			_currentIndex = startTokenId + quantity;
		}
		_afterTokenTransfers(address(0), to, startTokenId, 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.
     *
     * See {_mint}.
     *
     * Emits a {Transfer} event for each mint.
     */
	function _safeMint(
		address to,
		uint256 quantity,
		bytes memory _data
	) internal virtual {
		_mint(to, quantity);
		
		unchecked {
			if (to.code.length != 0) {
				uint256 end = _currentIndex;
				uint256 index = end - quantity;
				do {
					if (!_checkContractOnERC721Received(address(0), to, index++, _data)) {
						revert TransferToNonERC721ReceiverImplementer();
					}
				} while (index < end);
				// Reentrancy protection.
				if (_currentIndex != end) revert();
			}
		}
	}
	
	/**
	 * @dev Equivalent to `_safeMint(to, quantity, '')`.
     */
	function _safeMint(address to, uint256 quantity) internal virtual {
		_safeMint(to, quantity, '');
	}
	
	// =============================================================
	//                        BURN OPERATIONS
	// =============================================================
	
	/**
	 * @dev Equivalent to `_burn(tokenId, false)`.
     */
	function _burn(uint256 tokenId) internal virtual {
		_burn(tokenId, false);
	}
	
	/**
	 * @dev Destroys `tokenId`.
     * The approval is cleared when the token is burned.
     *
     * Requirements:
     *
     * - `tokenId` must exist.
     *
     * Emits a {Transfer} event.
     */
	function _burn(uint256 tokenId, bool approvalCheck) internal virtual {
		uint256 prevOwnershipPacked = _packedOwnershipOf(tokenId);
		
		address from = address(uint160(prevOwnershipPacked));
		
		(uint256 approvedAddressSlot, address approvedAddress) = _getApprovedSlotAndAddress(tokenId);
		
		if (approvalCheck) {
			// The nested ifs save around 20+ gas over a compound boolean condition.
			if (!_isSenderApprovedOrOwner(approvedAddress, from, _msgSenderERC721A()))
				if (!isApprovedForAll(from, _msgSenderERC721A())) revert TransferCallerNotOwnerNorApproved();
		}
		
		_beforeTokenTransfers(from, address(0), tokenId, 1);
		
		// Clear approvals from the previous owner.
		assembly {
			if approvedAddress {
			// This is equivalent to `delete _tokenApprovals[tokenId]`.
				sstore(approvedAddressSlot, 0)
			}
		}
		
		// Underflow of the sender's balance is impossible because we check for
		// ownership above and the recipient's balance can't realistically overflow.
		// Counter overflow is incredibly unrealistic as `tokenId` would have to be 2**256.
		unchecked {
		// Updates:
		// - `balance -= 1`.
		// - `numberBurned += 1`.
		//
		// We can directly decrement the balance, and increment the number burned.
		// This is equivalent to `packed -= 1; packed += 1 << _BITPOS_NUMBER_BURNED;`.
			_packedAddressData[from] += (1 << _BITPOS_NUMBER_BURNED) - 1;
		
		// Updates:
		// - `address` to the last owner.
		// - `startTimestamp` to the timestamp of burning.
		// - `burned` to `true`.
		// - `nextInitialized` to `true`.
			_packedOwnerships[tokenId] = _packOwnershipData(
				from,
				(_BITMASK_BURNED | _BITMASK_NEXT_INITIALIZED) | _nextExtraData(from, address(0), prevOwnershipPacked)
			);
		
		// If the next slot may not have been initialized (i.e. `nextInitialized == false`) .
			if (prevOwnershipPacked & _BITMASK_NEXT_INITIALIZED == 0) {
				uint256 nextTokenId = tokenId + 1;
				// If the next slot's address is zero and not burned (i.e. packed value is zero).
				if (_packedOwnerships[nextTokenId] == 0) {
					// If the next slot is within bounds.
					if (nextTokenId != _currentIndex) {
						// Initialize the next slot to maintain correctness for `ownerOf(tokenId + 1)`.
						_packedOwnerships[nextTokenId] = prevOwnershipPacked;
					}
				}
			}
		}
		
		emit Transfer(from, address(0), tokenId);
		_afterTokenTransfers(from, address(0), tokenId, 1);
		
		// Overflow not possible, as _burnCounter cannot be exceed _currentIndex times.
		unchecked {
			_burnCounter++;
		}
	}
	
	// =============================================================
	//                     EXTRA DATA OPERATIONS
	// =============================================================
	
	/**
	 * @dev Directly sets the extra data for the ownership data `index`.
     */
	function _setExtraDataAt(uint256 index, uint24 extraData) internal virtual {
		uint256 packed = _packedOwnerships[index];
		if (packed == 0) revert OwnershipNotInitializedForExtraData();
		uint256 extraDataCasted;
		// Cast `extraData` with assembly to avoid redundant masking.
		assembly {
			extraDataCasted := extraData
		}
		packed = (packed & _BITMASK_EXTRA_DATA_COMPLEMENT) | (extraDataCasted << _BITPOS_EXTRA_DATA);
		_packedOwnerships[index] = packed;
	}
	
	/**
	 * @dev Called during each token transfer to set the 24bit `extraData` field.
     * Intended to be overridden by the cosumer contract.
     *
     * `previousExtraData` - the value of `extraData` before transfer.
     *
     * Calling conditions:
     *
     * - When `from` and `to` are both non-zero, `from`'s `tokenId` will be
     * transferred to `to`.
     * - When `from` is zero, `tokenId` will be minted for `to`.
     * - When `to` is zero, `tokenId` will be burned by `from`.
     * - `from` and `to` are never both zero.
     */
	function _extraData(
		address from,
		address to,
		uint24 previousExtraData
	) internal view virtual returns (uint24) {}
	
	/**
	 * @dev Returns the next extra data for the packed ownership data.
     * The returned result is shifted into position.
     */
	function _nextExtraData(
		address from,
		address to,
		uint256 prevOwnershipPacked
	) private view returns (uint256) {
		uint24 extraData = uint24(prevOwnershipPacked >> _BITPOS_EXTRA_DATA);
		return uint256(_extraData(from, to, extraData)) << _BITPOS_EXTRA_DATA;
	}
	
	// =============================================================
	//                       OTHER OPERATIONS
	// =============================================================
	
	/**
	 * @dev Returns the message sender (defaults to `msg.sender`).
     *
     * If you are writing GSN compatible contracts, you need to override this function.
     */
	function _msgSenderERC721A() internal view virtual returns (address) {
		return msg.sender;
	}
	
	/**
	 * @dev Converts a uint256 to its ASCII string decimal representation.
     */
	function _toString(uint256 value) internal pure virtual returns (string memory str) {
		assembly {
		// The maximum value of a uint256 contains 78 digits (1 byte per digit),
		// but we allocate 0x80 bytes to keep the free memory pointer 32-byte word aliged.
		// We will need 1 32-byte word to store the length,
		// and 3 32-byte words to store a maximum of 78 digits. Total: 0x20 + 3 * 0x20 = 0x80.
			str := add(mload(0x40), 0x80)
		// Update the free memory pointer to allocate.
			mstore(0x40, str)
		
		// Cache the end of the memory to calculate the length later.
			let end := str
		
		// We write the string from rightmost digit to leftmost digit.
		// The following is essentially a do-while loop that also handles the zero case.
		// prettier-ignore
			for { let temp := value } 1 {} {
				str := sub(str, 1)
			// Write the character to the pointer.
			// The ASCII index of the '0' character is 48.
				mstore8(str, add(48, mod(temp, 10)))
			// Keep dividing `temp` until zero.
				temp := div(temp, 10)
			// prettier-ignore
				if iszero(temp) { break }
			}
			
			let length := sub(end, str)
		// Move the pointer 32 bytes leftwards to make room for the length.
			str := sub(str, 0x20)
		// Store the length.
			mstore(str, length)
		}
	}
}

/**
 * @dev Interface of ERC721AQueryable.
 */
interface IERC721AQueryable is IERC721A {
	/**
	 * Invalid query range (`start` >= `stop`).
	 */
	error InvalidQueryRange();
	
	/**
	 * @dev Returns the `TokenOwnership` struct at `tokenId` without reverting.
     *
     * If the `tokenId` is out of bounds:
     *
     * - `addr = address(0)`
     * - `startTimestamp = 0`
     * - `burned = false`
     * - `extraData = 0`
     *
     * If the `tokenId` is burned:
     *
     * - `addr = <Address of owner before token was burned>`
     * - `startTimestamp = <Timestamp when token was burned>`
     * - `burned = true`
     * - `extraData = <Extra data when token was burned>`
     *
     * Otherwise:
     *
     * - `addr = <Address of owner>`
     * - `startTimestamp = <Timestamp of start of ownership>`
     * - `burned = false`
     * - `extraData = <Extra data at start of ownership>`
     */
	function explicitOwnershipOf(uint256 tokenId) external view returns (TokenOwnership memory);
	
	/**
	 * @dev Returns an array of `TokenOwnership` structs at `tokenIds` in order.
     * See {ERC721AQueryable-explicitOwnershipOf}
     */
	function explicitOwnershipsOf(uint256[] memory tokenIds) external view returns (TokenOwnership[] memory);
	
	/**
	 * @dev Returns an array of token IDs owned by `owner`,
     * in the range [`start`, `stop`)
     * (i.e. `start <= tokenId < stop`).
     *
     * This function allows for tokens to be queried if the collection
     * grows too big for a single call of {ERC721AQueryable-tokensOfOwner}.
     *
     * Requirements:
     *
     * - `start < stop`
     */
	function tokensOfOwnerIn(
		address owner,
		uint256 start,
		uint256 stop
	) external view returns (uint256[] memory);
	
	/**
	 * @dev Returns an array of token IDs owned by `owner`.
     *
     * This function scans the ownership mapping and is O(`totalSupply`) in complexity.
     * It is meant to be called off-chain.
     *
     * See {ERC721AQueryable-tokensOfOwnerIn} for splitting the scan into
     * multiple smaller scans if the collection is large enough to cause
     * an out-of-gas error (10K collections should be fine).
     */
	function tokensOfOwner(address owner) external view returns (uint256[] memory);
}

/**
 * @title ERC721AQueryable.
 *
 * @dev ERC721A subclass with convenience query functions.
 */
abstract contract ERC721AQueryable is ERC721A, IERC721AQueryable {
	/**
	 * @dev Returns the `TokenOwnership` struct at `tokenId` without reverting.
     *
     * If the `tokenId` is out of bounds:
     *
     * - `addr = address(0)`
     * - `startTimestamp = 0`
     * - `burned = false`
     * - `extraData = 0`
     *
     * If the `tokenId` is burned:
     *
     * - `addr = <Address of owner before token was burned>`
     * - `startTimestamp = <Timestamp when token was burned>`
     * - `burned = true`
     * - `extraData = <Extra data when token was burned>`
     *
     * Otherwise:
     *
     * - `addr = <Address of owner>`
     * - `startTimestamp = <Timestamp of start of ownership>`
     * - `burned = false`
     * - `extraData = <Extra data at start of ownership>`
     */
	function explicitOwnershipOf(uint256 tokenId) public view virtual override returns (TokenOwnership memory) {
		TokenOwnership memory ownership;
		if (tokenId < _startTokenId() || tokenId >= _nextTokenId()) {
			return ownership;
		}
		ownership = _ownershipAt(tokenId);
		if (ownership.burned) {
			return ownership;
		}
		return _ownershipOf(tokenId);
	}
	
	/**
	 * @dev Returns an array of `TokenOwnership` structs at `tokenIds` in order.
     * See {ERC721AQueryable-explicitOwnershipOf}
     */
	function explicitOwnershipsOf(uint256[] calldata tokenIds)
	external
	view
	virtual
	override
	returns (TokenOwnership[] memory)
	{
		unchecked {
			uint256 tokenIdsLength = tokenIds.length;
			TokenOwnership[] memory ownerships = new TokenOwnership[](tokenIdsLength);
			for (uint256 i; i != tokenIdsLength; ++i) {
				ownerships[i] = explicitOwnershipOf(tokenIds[i]);
			}
			return ownerships;
		}
	}
	
	/**
	 * @dev Returns an array of token IDs owned by `owner`,
     * in the range [`start`, `stop`)
     * (i.e. `start <= tokenId < stop`).
     *
     * This function allows for tokens to be queried if the collection
     * grows too big for a single call of {ERC721AQueryable-tokensOfOwner}.
     *
     * Requirements:
     *
     * - `start < stop`
     */
	function tokensOfOwnerIn(
		address owner,
		uint256 start,
		uint256 stop
	) external view virtual override returns (uint256[] memory) {
		unchecked {
			if (start >= stop) revert InvalidQueryRange();
			uint256 tokenIdsIdx;
			uint256 stopLimit = _nextTokenId();
		// Set `start = max(start, _startTokenId())`.
			if (start < _startTokenId()) {
				start = _startTokenId();
			}
		// Set `stop = min(stop, stopLimit)`.
			if (stop > stopLimit) {
				stop = stopLimit;
			}
			uint256 tokenIdsMaxLength = balanceOf(owner);
		// Set `tokenIdsMaxLength = min(balanceOf(owner), stop - start)`,
		// to cater for cases where `balanceOf(owner)` is too big.
			if (start < stop) {
				uint256 rangeLength = stop - start;
				if (rangeLength < tokenIdsMaxLength) {
					tokenIdsMaxLength = rangeLength;
				}
			} else {
				tokenIdsMaxLength = 0;
			}
			uint256[] memory tokenIds = new uint256[](tokenIdsMaxLength);
			if (tokenIdsMaxLength == 0) {
				return tokenIds;
			}
		// We need to call `explicitOwnershipOf(start)`,
		// because the slot at `start` may not be initialized.
			TokenOwnership memory ownership = explicitOwnershipOf(start);
			address currOwnershipAddr;
		// If the starting slot exists (i.e. not burned), initialize `currOwnershipAddr`.
		// `ownership.address` will not be zero, as `start` is clamped to the valid token ID range.
			if (!ownership.burned) {
				currOwnershipAddr = ownership.addr;
			}
			for (uint256 i = start; i != stop && tokenIdsIdx != tokenIdsMaxLength; ++i) {
				ownership = _ownershipAt(i);
				if (ownership.burned) {
					continue;
				}
				if (ownership.addr != address(0)) {
					currOwnershipAddr = ownership.addr;
				}
				if (currOwnershipAddr == owner) {
					tokenIds[tokenIdsIdx++] = i;
				}
			}
		// Downsize the array to fit.
			assembly {
				mstore(tokenIds, tokenIdsIdx)
			}
			return tokenIds;
		}
	}
	
	/**
	 * @dev Returns an array of token IDs owned by `owner`.
     *
     * This function scans the ownership mapping and is O(`totalSupply`) in complexity.
     * It is meant to be called off-chain.
     *
     * See {ERC721AQueryable-tokensOfOwnerIn} for splitting the scan into
     * multiple smaller scans if the collection is large enough to cause
     * an out-of-gas error (10K collections should be fine).
     */
	function tokensOfOwner(address owner) external view virtual override returns (uint256[] memory) {
		unchecked {
			uint256 tokenIdsIdx;
			address currOwnershipAddr;
			uint256 tokenIdsLength = balanceOf(owner);
			uint256[] memory tokenIds = new uint256[](tokenIdsLength);
			TokenOwnership memory ownership;
			for (uint256 i = _startTokenId(); tokenIdsIdx != tokenIdsLength; ++i) {
				ownership = _ownershipAt(i);
				if (ownership.burned) {
					continue;
				}
				if (ownership.addr != address(0)) {
					currOwnershipAddr = ownership.addr;
				}
				if (currOwnershipAddr == owner) {
					tokenIds[tokenIdsIdx++] = i;
				}
			}
			return tokenIds;
		}
	}
}

contract CryptoCanyonHeroes is ERC721AQueryable, AccessControl {
	
	string public _baseTokenURI = "https://api.gamesfi.live/erc721/token/";
	
	bytes32 public constant MINTER_ROLE = keccak256("MINTER_ROLE");
	
	address public upgradedToAddress = address(0);
	
	constructor() ERC721A("Crypto Canyon Heros", "CCH") {
		_setupRole(DEFAULT_ADMIN_ROLE, _msgSender());
		_setupRole(MINTER_ROLE, _msgSender());
	}
	
	function getCurrentTokenId() external view returns (uint256) {
		return _nextTokenId();
	}
	
	function upgrade(address _upgradedToAddress) external {
		require(
			hasRole(DEFAULT_ADMIN_ROLE, _msgSender()),
			"Caller is not a admin"
		);
		
		upgradedToAddress = _upgradedToAddress;
	}
	
	/**
	 * @dev See {IERC165-supportsInterface}.
     */
	
	function supportsInterface(bytes4 interfaceId)
	public
	view
	virtual
	override(AccessControl, ERC721A, IERC721A)
	returns (bool)
	{
		return
			interfaceId == type(IAccessControl).interfaceId ||
			interfaceId == type(IERC721A).interfaceId ||
			interfaceId == 0x01ffc9a7 || // ERC165 interface ID for ERC165.
			interfaceId == 0x80ac58cd || // ERC165 interface ID for ERC721.
			interfaceId == 0x5b5e139f || // ERC165 interface ID for ERC721Metadata.
			super.supportsInterface(interfaceId);
	}
	
	function setBaseURI(string calldata baseURI) external {
		require(
			hasRole(DEFAULT_ADMIN_ROLE, _msgSender()),
			"unauthorized access"
		);
		_baseTokenURI = baseURI;
	}
	
	function mint(address to, uint256 size) external returns (bool) {
		require(
			address(0) == upgradedToAddress,
			"Contract upgraded to new address"
		);
		require(hasRole(MINTER_ROLE, _msgSender()), "Caller is not a minter");
		require(to != address(0), "can't mint to empty address");
		require(size > 0, "size must greater than zero");
		_mint(to, size);
		return true;
	}
	
	function _baseURI() internal view virtual override returns (string memory) {
		return _baseTokenURI;
	}
}