abstract contract ERC721TradableBurnable is ERC721, ContextMixin, ERC721Burnable, NativeMetaTransaction, Ownable {
    using SafeMath for uint256;
    using Counters for Counters.Counter;


    Counters.Counter private _nextTokenId;
    address proxyRegistryAddress;

    constructor(
        string memory _name,
        string memory _symbol,
        address _proxyRegistryAddress
    ) ERC721(_name, _symbol) {
        proxyRegistryAddress = _proxyRegistryAddress;
        // nextTokenId is initialized to 1, since starting at 0 leads to higher gas cost for the first minter
        _nextTokenId.increment();
        _initializeEIP712(_name);
    }

    /**
     * @dev Mints a token to an address with a tokenURI.
     * @param _to address of the future owner of the token
     */
    function mintTo(address _to) internal {
        uint256 currentTokenId = _nextTokenId.current();
        _nextTokenId.increment();
        _safeMint(_to, currentTokenId);
    }

    /**
        @dev Returns the total tokens minted so far.
        1 is always subtracted from the Counter since it tracks the next available tokenId.
     */
    function totalSupply() public view returns (uint256) {
        return _nextTokenId.current() - 1;
    }

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

        return super.isApprovedForAll(owner, operator);
    }

    /**
     * This is used instead of msg.sender as transactions won't be sent by the original token owner, but by OpenSea.
     */
    function _msgSender()
        internal
        override
        view
        returns (address sender)
    {
        return ContextMixin.msgSender();
    }
}
/**
 * @title ERC721TradableBurnable
 * ERC721TradableBurnable - ERC721 contract that whitelists a trading address, and has minting functionality.
 */
function _msgSender()
    internal
    override
    view
    returns (address sender)
{
    return ContextMixin.msgSender();
}

/**
 * This is used instead of msg.sender as transactions won't be sent by the original token owner, but by OpenSea.
 */