poj2665

简单题

#include <iostream>
#include <cstdlib>
#include <cstring>
#include <cstdio>
using namespace std;

int main()
{
    //freopen("D:\\t.txt", "r", stdin);
    int l, m;
    while (scanf("%d%d", &l, &m) != EOF && !(l == 0 && m == 0))
    {
        int ans = l + 1;
        for (int i = 0; i < m; i++)
        {
            int a, b;
            scanf("%d%d", &a, &b);
            ans -= b - a + 1;
        }
        printf("%d\n", ans);
    }
    return 0;
}