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 Tells the type of proxy (EIP 897)
     * @return Type of proxy, 2 for upgradeable proxy
     */
    function proxyType() public pure returns (uint256 proxyTypeId);

    /**
     * @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));

        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 implementation() public view returns (address);

/**
 * @dev Tells the address of the implementation where every call will be delegated.
 * @return address of the implementation to which it will be delegated
 */