https://blog.gongquiz.com/2021/11/25/%eb%8b%a4%ec%9d%8c-cnc-%ed%94%84%eb%a1%9c%ea%b7%b8%eb%9e%a8%ec%9d%98-%ed%9a%8c%ec%a0%84%ec%88%98%eb%8a%94-%ec%95%bd-%ec%96%bc%eb%a7%88%ec%9d%b8%ea%b0%80-%ec%bb%b4%ed%93%a8%ed%84%b0%ec%9d%91/