https://blog.gongquiz.com/2022/11/25/%ec%a0%80%eb%a8%bc-%ec%8b%a4%eb%b2%84german-silver%ec%97%90-%eb%8c%80%ed%95%9c-%ec%84%a4%eb%aa%85-%ec%a4%91-%ed%8b%80%eb%a6%b0-%ea%b2%83%ec%9d%80-%ea%b7%80%ea%b8%88%ec%86%8d%ea%b0%80%ea%b3%b5/