2. Own a(n) Storage Pin NFT

// SPDX-License-Identifier: MIT
pragma solidity ^0.8.13;

contract EmployeeStorage {
    error TooManyShares(uint _updatedShares);

    // Packing tối ưu: shares (2 bytes) + salary (3 bytes) trong slot 0
    uint16 private shares;
    uint24 private salary;
    uint256 public idNumber;
    string public name;

    constructor(uint16 _shares, string memory _name, uint24 _salary, uint256 _idNumber) {
        shares = _shares;
        name = _name;
        salary = _salary;
        idNumber = _idNumber;
    }

    function viewSalary() external view returns (uint24) {
        return salary;
    }

    function viewShares() external view returns (uint16) {
        return shares;
    }

    function grantShares(uint16 _newShares) external {
        require(_newShares < 5001, "Too many shares");
        uint16 _updatedShares = shares + _newShares;
        if (_updatedShares > 5000) {
            revert TooManyShares(_updatedShares);
        }
        shares = _updatedShares;
    }

    function checkForPacking(uint _slot) public view returns (uint r) {
        assembly {
            r := sload(_slot)
        }
    }

    function debugResetShares() public {
        shares = 1000;
    }
}