WA
by zMinYu @ 2023-03-31 18:01:54
```cpp
for(int x1=1;x1<=n;x1++)
for(int x2=x1;x2<=n;x2++)
for(int y1=1;y1<=n;y1++)
for(int y2=y1;y2<=n;y2++)
```
注意 $x2$ 和 $y2$ 的初值
by HY248 @ 2023-03-31 18:29:29
@[HY248](/user/383638) 谢谢啊！
by zMinYu @ 2023-04-01 08:20:44