代码如下

呃呃呃```

#include<iostream>
using namespace std;
int main(){
	int q[10001]={},n,count,a,b,c;
	cin>>n>>c;
	while(c>0){
		cin>>a>>b;
		for(int i=a;i<=b;i++){
			q[i]=1;
		}
		c--;
	}
	for(int e=0;e<n;e++){
		if(q[e]==0){
			count++;
		}
	}
	cout<<count+1;
	return 0;
}