```cpp
for(int i=l;i<=r;i++)if(f(i))ans++;
```
和外层的i重名了
by Frost2008 @ 2022-03-01 21:06:09
另：没有特判0和1和负数
by Frost2008 @ 2022-03-01 21:07:23
**** _还是错了_ ****
```
#include<bits/stdc++.h>
using namespace std;
bool f(int x)
{
if(x==1)return false;
for(int i=2;i<sqrt(x);i++)
if(x%i==0) return false;
return true;
}
int main()
{
int l,r,n,m;
cin>>n>>m;
for(int i=1;i<=n;i++)
{
cin>>l>>r;
if(l<0&&r>=m) {
cout<<"Crossing the line"<<endl;
continue;
}
int ans=0;
for(int j=l;j<=r;j++)if(f(j))ans++;
cout<<ans<<endl;
}
return 0;
}
```
[链接](https://www.luogu.com.cn/record/70371056)
by hhb0422 @ 2022-03-01 21:13:48
l<1||r>m
by Frost2008 @ 2022-03-01 21:15:36
不用筛法也会超时的吧
by LeslieKang @ 2022-03-09 14:52:40
@[Yuki_S2008](/user/495053) l<1||l>m||r<1||r>m
by inkpigeon @ 2022-07-17 17:10:13
@[hhb0422](/user/543760) 换成线性筛（欧拉筛）
by inkpigeon @ 2022-07-17 17:11:07