sydobd

pragma solidity ^0.8.1;

import "https://github.com/OpenZeppelin/openzeppelin-contracts/blob/master/contracts/utils/math/SafeMath.sol";

contract Allowance {
    address owner;
    mapping(address => uint) public allowance;
    
    //using library
    using SafeMath for uint;

sydobd

pragma solidity ^0.5.17;

contract StartStopUpdate{
    
    address owner;
    
    constructor() public{
        owner = msg.sender;
    }