NUIST P1350 P1351 差分

#include <iostream>
#include <cstring>
#include <algorithm>
#define MAXN 100010
#define MAXM 100010
using namespace std;
int n,m,l,r,a,b;
int sec[MAXN];
int main() 
{
	while (scanf("%d%d",&n,&m)!=EOF)
	{
		memset(sec,0,sizeof(sec));
	for (int i=1;i<=m;i++) {
		scanf("%d%d",&l,&r);
		sec[l]++;
		sec[r+1]--;
	}
	scanf("%d%d",&a,&b);
	
	for (int i=1;i<=b;i++)
	sec[i]+=sec[i-1];
	for (int i=a+1;i<=b;i++)
	sec[i]+=sec[i-1];
	printf("%d\n",sec[b]);
	}
	return 0;
	
}