https://blog.gongquiz.com/2021/10/12/%eb%b9%84%ed%96%89%ea%b8%b0%ec%9d%98-%ed%82%a4%eb%8f%8c%ec%9d%b4loop-%eb%b9%84%ed%96%89-%ec%8b%9c-%eb%b9%84%ed%96%89%ea%b8%b0%ec%97%90-%ec%9e%91%ec%9a%a9%ed%95%98%eb%8a%94-%ed%95%98%ec%a4%91/