https://blog.wongcw.com/2022/07/19/imo-2022-%e6%88%90%e7%b8%be%e5%85%ac%e4%bd%88%ef%bc%9a%e4%b8%ad%e5%9c%8b%e9%9a%8a%e9%80%a3%e7%ba%8c%e4%b8%89%e5%b9%b4%e8%9f%ac%e8%81%af%e5%86%a0%e8%bb%8d6%e4%ba%ba%e5%85%a8%e9%83%a8%e6%bb%bf%e5%88%86/