#include <iostream>
#include <vector>
#include <algorithm>
using namespace std;

int main()
{
    cin.tie(nullptr);
    cout.tie(nullptr);
    ios_base::sync_with_stdio(false);
    int n, m;
    cin >> n >> m;
    vector<int>vec(n+1);
    for (size_t i = 0; i < m; i++)
    {
        int a, b;
        cin >> a >> b;
        vec[a]++;
        vec[b]--;
    }
    int c = 0, s = 0, p = 0;
    for (size_t i = 1; i < n + 1; i++)
    {
        s += vec[i];
        if (s != 0 && p == 0)c++;
        p = s;
    }
    cout << c << endl;
    return 0;
}
/*
10 4
8 9
1 6
1 3
3 4
-2
*/