# 这是代码
```cpp
#include<bits/stdc++.h>
using namespace std;
int f[100001];
int main()
{
int n,m,x,y,sum=0;
cin>>n>>m;
for(int i=1;i<=m;i++)
{
cin>>x>>y;
for(int j=x;j<=y;j++)f[j]=1;
}
for(int i=0;i<=n;i++)
{
if(f[i]==0)sum++;
}
cout<<sum;
return 0;
}
```
by imzfx_Spuare @ 2023-03-19 10:34:14
# 这里
```cpp
if (a[k]==1) cnt+=1;
```
### 因改为
```
if (a[k]==0) cnt+=1;
```
by imzfx_Spuare @ 2023-03-19 10:36:15
# 还有这
```cpp
for (int k=1;k<=l;k++)
```
## 因改为
```
for (int k=0;k<=l;k++)
```
by imzfx_Spuare @ 2023-03-19 10:39:20
因为0也可以种树
by imzfx_Spuare @ 2023-03-19 10:41:24
@[a15061696189](/user/671481) 感谢！
by Hanser_0019 @ 2023-03-20 15:38:16