http://192.168.22.15:9997/problem.php?cid=1154&pid=0
https://www.luogu.org/problem/P3959
https://www.luogu.org/blog/m-sea/qian-tan-SA
http://192.168.22.15:9997/problem.php?cid=1154&pid=0
https://www.luogu.org/problem/P3959
https://www.luogu.org/blog/m-sea/qian-tan-SA