#include <iostream>
#include <vector>
#include <time.h>
using namespace std;


int main()
{
	ios_base::sync_with_stdio(false);
	cin.tie(NULL);
	cout.tie(NULL);
	int n, m;
	cin >> n >> m;
	vector<int> vec(n+1, 0);
	for (size_t i = 0; i < m; i++)
	{
		int a, b;
		cin >> a >> b;
		vec[a]++;
		vec[b]--;
	}
	int ossz = 0;
	int db = 0;
	for (size_t i = 1; i < n; i++)
	{
		ossz += vec[i];
		if (ossz == 0)
		{
			db++;
		}
	}
	cout << db << endl;
}
/*
10 4
8 9
1 6
1 3
3 4
*/