https://blog.gongquiz.com/2021/07/22/%eb%8b%a4%ec%9d%8c-%ec%a4%91-2%ec%9b%90-%ec%a0%84%ec%86%a1-%eb%b6%80%ed%98%b8%ec%9d%b8-nrz%ec%9d%98-%ec%84%a4%eb%aa%85%ec%9c%bc%eb%a1%9c-%ed%8b%80%eb%a6%b0-%ea%b2%83%ec%9d%80-%ec%a0%95%eb%b3%b4/