已经有人发过了，建议紫衫
by OIer_Tan @ 2024-04-08 16:57:33
不是加一个mod就行了吗
```cpp
(a-b+mod)%mod
```
by tjx114514 @ 2024-04-08 17:20:12
@[tjx114514](/user/1059849) %%%
by qidaimuhuoying @ 2024-04-08 17:25:50
@[qidaimuhuoying](/user/1039740) https://www.luogu.com.cn/discuss/797570
by tjx114514 @ 2024-04-08 17:32:26