https://blog.gongquiz.com/2021/01/21/%eb%8b%a4%ec%9d%8c-%ec%a4%91-%eb%b0%9c%ed%99%94%eb%8f%84-g1%ec%9d%98-%eb%b0%9c%ed%99%94%ec%a0%90%ec%9d%98-%eb%b2%94%ec%9c%84%eb%a1%9c-%ec%98%b3%ec%9d%80-%ea%b2%83%ec%9d%80-%ec%82%b0%ec%97%85/