题目背景

本题可能不存在正确解法，题解均已被 hack。

https://www.luogu.com.cn/record/198294955 https://www.luogu.com.cn/record/198001008 https://www.luogu.com.cn/record/191936939 https://www.luogu.com.cn/record/189661310 https://www.luogu.com.cn/record/187824007

代码长度总一样，缘分缘分啊