poj 2665 Trees

#include <iostream>#include <cstdlib>#include <cstring>#include <cstdio>using namespace std;int main(){    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("%dn", ans);    }    return 0;}