pragma solidity ^0.4.20;

contract sum{

? ? uint balance;

? ? function update (uint amount) public returns (identity, uint){

? ? ? ? balance+=amount;

? ? ? ? return (msg.sender, balance);

? ? }

? ? function get() public view returns (uint) {

? ? ? ? return balance;

? ? }

}

pragma solidity >=0.4.0 <0.7.0;

contract SimpleStorage {

uint storedData;

function set(uint x) public {

? storedData = x;

}

function get() public view returns (uint) {

? return storedData;

}

}