https://blog.gongquiz.com/2021/01/12/%ec%9e%ac%eb%a3%8c%ec%97%90-%ea%b5%ac%eb%a9%8d%ec%9d%b4-%ec%9e%88%ea%b1%b0%eb%82%98-%eb%85%b8%ec%b9%98notch-%eb%93%b1%ec%9d%b4-%ec%9e%88%eb%8a%94-%ec%9e%ac%eb%a3%8c%ec%97%90-%ec%99%b8%eb%a0%a5/