铜球
by xzggzh1 @ 2021-03-22 19:50:18
~~打表~~
by lahlah @ 2021-04-07 08:49:22
[也许是这样](https://www.luogu.com.cn/blog/neutral/convex-property-proof)（但我感觉有点伪。）
by Neutralized @ 2022-07-20 10:39:34