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contracts...SimpleStorage.sol

// SPDX-License-Identifier: MIT
pragma solidity >=0.6.0 <0.9.0;

contract SimpleStorage {
    
    uint256 public favoriteNumber;
    
    struct People {
        uint256 favoriteNumber;
        string name;
    }
    
    mapping(string => uint256) public nameToFavoriteNumbers;
    
    People[] public people;
    
    function store(uint256 _favoriteNumber) public {
        favoriteNumber = _favoriteNumber;
    }
    
    function retrieve(uint256 retrived) public view returns(uint256) {
        assert(retrived <= favoriteNumber);
        return favoriteNumber - retrived;
    }
    
    function addPerson(string memory _name, uint256 _favoriteNumber) public {
        people.push(People({
            favoriteNumber: _favoriteNumber,
            name: _name
        }));
        nameToFavoriteNumbers[_name] = _favoriteNumber;
    }
    
}