[记作后面](http://172.30.1.16/upload/image/20171115/20171115165652_23158.jpg)
by CatLord @ 2022-09-29 19:05:18
这题？[B2104](https://www.luogu.com.cn/problem/B2104)
by ivoleuoy @ 2022-09-29 19:13:55