https://www.luogu.com.cn/record/80057521 and https://www.luogu.com.cn/blog/user27324/solution-p2024
https://www.luogu.com.cn/record/79776618 and https://www.luogu.com.cn/blog/McHf/solution-cf343c
还有一些 coci 提交没找到出处，但码风都不一样。
