#include<stdio.h>
#include<string.h>
int s[10000];
int main() {
	int l,m;
	int cnt=0;
	scanf("%d %d", &l, &m);
	memset(s, 1, sizeof(int) * (l+1));
	printf("%d", s[l]);
	for (int i = 0; i < m; i++) {
		int u, v;
		scanf("%d %d", &u, &v);
		for (; u <= v; u++) {
			s[u] = 0;
		}
	}
	for (int i = 0; i < l+1; i++) {
		if (s[i])cnt++;
	}
	printf("%d\n", cnt);
	return 0;
}