pragma solidity >=0.4.22 <0.7.0; contract HappyMath { address owner; uint storedData; constructor() public { owner = msg.sender; storedData = 10; } modifier onlyOwner() { require(msg.sender == owner, "Only owner can know the result"); _; } function sum(uint a, uint b) onlyOwner public view returns(uint){ uint result = a + b + storedData; return result; } function kill() public { require(msg.sender == owner); selfdestruct(msg.sender); } }