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HelloWorld.sol

//SPDX-License-Identifier: Unlicense
pragma solidity ^0.8.0;

// Start of contact
contract HelloWorld {

    // Storage (state) variable
    uint private Number;

    // Return the value of storage variable
    function retrieveNumber() public view returns (uint) {
        return Number;
    }

    // Change storage (state) variable
    function storeNumber(uint _Number) public {
        Number = _Number;
    }
}