#include<bits/stdc++.h>
using namespace std;
const int N = 1e5 + 10;
int a[N];
int main()
{
	int n,m;
	cin>>n>>m;
	for(int i = 0,l,r ; i < m ;i++)
	{
		cin >> l >> r;
		for(int j = l ; j <= r ; j++)
		{
			a[j] = 1;
		}
	}
	int ans = 0;
	for(int i = 0 ; i <= n ; i++ )
	{
		if(a[i] == 0)
			ans++;
	}
	cout << ans << endl;
	return 0;
}

#include<iomanip>
#include<cmath>
#include<cstring>
using namespace std;
const int N=1e5+10;
const int INF=0x3f3f3f3f;
int l,m,x,y,ans;
bool a[N];
int main()
{
	cin>>l>>m;
	while(m--)
	{
		cin>>x>>y;
		for(int i=x;i<=y;i++)
		a[i]=1;
	}
	for(int i=0;i<=l;i++)
	{
		if(!a[i])
		ans++;
	}
	cout<<ans;
    return 0;
}

for (int i = 0; i <= l; i++)
    a[i] = 1;

while (n--) {
    int s, e;
    cin >> s >> e;

    for (int i = s; i <= e; i++)
        a[i] = 0;
}

int ans = 0;

for (int i = 0; i <= l; i++)
    ans += a[i];

cout << ans << endl;
return 0;

for (int i = 0; i <= l; i++)
    a[i] = 1;

while (n--) {
    int s, e;
    cin >> s >> e;

    for (int i = s; i <= e; i++)
        a[i] = 0;
}

int ans = 0;

for (int i = 0; i <= l; i++)
    ans += a[i];

cout << ans << endl;
return 0;

for (int i = 0; i <= l; i++)
    a[i] = 1;

while (n--) {
    int s, e;
    cin >> s >> e;

    for (int i = s; i <= e; i++)
        a[i] = 0;
}

int ans = 0;

for (int i = 0; i <= l; i++)
    ans += a[i];

cout << ans << endl;
return 0;

for (int i = 0; i <= l; i++)
    a[i] = 1;

while (n--) {
    int s, e;
    cin >> s >> e;

    for (int i = s; i <= e; i++)
        a[i] = 0;
}

int ans = 0;

for (int i = 0; i <= l; i++)
    ans += a[i];

cout << ans << endl;
return 0;

#include<bits/stdc++.h>
using namespace std;
int main(){
	int L,sum=0;
	cin>>L;
	int a[10001]={};
	int M;
	cin>>M;
	int x,y;
	for(int i=0;i<M;i++){
		cin>>x>>y;
		for(int j=x;j<=y;j++){
			a[j]=1;
		}
	}
	for(int i=0;i<=L;i++){
		if(a[i]==0){
			sum++;
		}
	}
	cout<<sum;
	return 0;
}
```

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# 信息


递交者![](http://cn.gravatar.com/avatar/190c4015cc8e9d4a9ea1ae5d1f5423b2?d=mm&s=64) [尹晨恩 (yinchenen) ](http://temege.com/user/3744)[LV 4](http://temege.com/user/3744)题目[**P677**  校门外的树](http://temege.com/p/677)语言C++ 11递交时间**4 分钟前**分数100总耗时7ms峰值内存312 KiB





# 状态

* [评测队列](http://temege.com/record)
* [服务状态](http://temege.com/status)



# 开发

* [开源](https://github.com/hydro-dev/Hydro)

```

#include<stdio.h>
#include<iostream>
using namespace std; 
const int N=1e4+10;
const int INF=0x3f3f3f3f; 
int L,M,sum;        
bool a[N];

int main()
{
    cin>>L>>M;
    for(int i=1;i<=M;i++)
    {
    	int x,y;
    	cin>>x>>y;
		for(int j=x;j<=y;j++)
			a[j]=1;
	}
    
	for(int i=0;i<=L;i++)
    	if(a[i]==0)
        	sum++;
        
    cout<<sum;
    return 0;
}

}
int sum = 0;
for(int i =0 ; i <= n ; i++)
    if(a[i] == 0)
        sum++;
cout << sum << endl;

#include <bits/stdc++.h>
using namespace std;

int main() {
    int a [10010];
    int l, n;
    cin >> l >> n;

    for (int i = 0; i <= l; i++)
        a[i] = 1;

    while (n--) {
        int s, e;
        cin >> s >> e;

        for (int i = s; i <= e; i++)
            a[i] = 0;
    }

    int ans = 0;

    for (int i = 0; i <= l; i++)
        ans += a[i];

    cout << ans << endl;
    return 0;
}

int a [10010];

int l, n;

cin >> l >> n;

for (int i = 0; i <= l; i++)

    a[i] = 1;

while (n--) {

    int s, e;

    cin >> s >> e;

    for (int i = s; i <= e; i++)

        a[i] = 0;

}

int ans = 0;

for (int i = 0; i <= l; i++)

    ans += a[i];

cout << ans << endl;

return 0;