https://www.luogu.com.cn/blog/greenlcat/solution-p1600
https://www.cnblogs.com/bingdada/p/7744200.html
https://blog.csdn.net/weixin_30911809/article/details/101790074
前前后后认认真真看了三篇博客才终于明白了大概
醉了，醉了
原文：https://www.cnblogs.com/caterpillor/p/13179676.html