$down$ 里面的懒标记有错。
```cpp
mark[p*2]=mark[p*2]*mark2[p]+mark[p];
mark[p*2+1]=mark[p*2+1]*mark2[p]+mark[p];
```
by gxxjqqiang @ 2024-03-04 18:54:18
直接加会把之前的乘给漏算
by gxxjqqiang @ 2024-03-04 18:55:10
感谢
by czy0407 @ 2024-03-04 20:26:12