contract.box.sol

// contracts/Box.sol
// SPDX-License-Identifier: MIT
pragma solidity ^0.8.0;
import "@openzeppelin/contracts/access/Ownable.sol";
contract Box is Ownable {
  uint256 private value;
// Emitted when the stored value changes
  event ValueChanged(uint256 newValue);
// Stores a new value in the contract
  function store(uint256 newValue) public onlyOwner {
    value = newValue;
    emit ValueChanged(newValue);
  }
// Reads the last stored value
  function retrieve() public view returns (uint256) {
    return value;
  }
}