contract Proxy {
    /**
    * @dev Tells the address of the implementation where every call will be delegated.
    * @return address of the implementation to which it will be delegated
    */
    function implementation() public view returns (address);

    /**
    * @dev Fallback function allowing to perform a delegatecall to the given implementation.
    * This function will return whatever the implementation call returns
    */
    function () public payable {
        address _impl = implementation();
        require(_impl != address(0), "address invalid");

        assembly {
            let ptr := mload(0x40)
            calldatacopy(ptr, 0, calldatasize)
            let result := delegatecall(gas, _impl, ptr, calldatasize, 0, 0)
            let size := returndatasize
            returndatacopy(ptr, 0, size)

            switch result
            case 0 { revert(ptr, size) }
            default { return(ptr, size) }
        }
    }
}
/**
 * @title Proxy
 * @dev Gives the possibility to delegate any call to a foreign implementation.
 */
function () public payable {
        address _impl = implementation();
        require(_impl != address(0), "address invalid");

        assembly {
            let ptr := mload(0x40)
            calldatacopy(ptr, 0, calldatasize)
            let result := delegatecall(gas, _impl, ptr, calldatasize, 0, 0)
            let size := returndatasize
            returndatacopy(ptr, 0, size)

            switch result
            case 0 { revert(ptr, size) }
            default { return(ptr, size) }
        }
    }
/**
 * @dev Fallback function allowing to perform a delegatecall to the given implementation.
 * This function will return whatever the implementation call returns
 */