/
NOIP2005复赛 普及组 第2题 校门外的树(枚举)
http://noi.openjudge.cn/ch0106/06/
https://www.luogu.org/problemnew/show/P1047
https://bbs.codeaha.com/problem-12002.html
/
#include <iostream>
using namespace std;

int road[10001];

int main()
{
int l, m, s, e, cnt = 0;
cin >> l >> m;

for (int i = 0; i <= l; i++) road[i] = 1;for (int i = 0; i < m; i++){ cin >> s >> e; for (int j = s; j <= e; j++) //start end road[j] = 0;}for (int i = 0; i <= l; i++) if (road[i] == 1) cnt++;cout << cnt; return 0;

}