2011清华考研机试题1

题目描述
[url]http://ac.jobdu.com/problem.php?id=1088[/url]
水~

#include <iostream>
using namespace std;
int main()
{
	int l,m;
	int trees[10008];
	while(cin>>l>>m)
	{
		int i,j,ans=0;
		for(i=0;i<=l;i++)
			trees[i]=0;
		for(i=0;i<m;i++)
		{
			int a,b;
			cin>>a>>b;
			for(j=a;j<=b;j++)
				trees[j]=1;
		}
		for(i=0;i<=l;i++)
			if(trees[i]==0)
				ans++;
		cout<<ans<<endl;

	}
	return 0;
}