树是0到l 所以是≤l 而非 <l
by hjqhs @ 2023-05-07 18:30:12
```c
#include<bits/stdc++.h>
using namespace std;
int N[100010];
int main()
{
int L,m,sum=0,a,b;
cin>>L>>m;
for(int i=1;i<=m;i++)
{
cin>>a>>b;
for(int j=a;j<=b;j++) N[j]=1;
}
for(int i=0;i<=L;i++)
{
if(N[i]==0)
{
sum++;
}
}
cout<<sum;
return 0;
}
```
by ALexYjy___ @ 2023-05-07 20:40:13