// UUID: f1b9e09d-179f-4215-a222-e504955294dc
#include <bits/stdc++.h>
using usll = unsigned long long;
using namespace std;

int main() {
    ios::sync_with_stdio(false);
    ios_base::sync_with_stdio(false);
    cin.tie(nullptr);
    
    int n = 0, m = 0, sum = 0;
    cin >> n >> m;
    vector<int> szakasz(n, 0);

    for(int i = 0; i < m; i++) {
        int a,b;
        cin >> a >> b;
        szakasz[a-1]++;
        szakasz[b-1]--;
    }

    int cnt = 0, prev = 0;
    for(int i = 0; i < n; i++) {
        cnt+=szakasz[i];
        if (cnt == 0 && prev != 0) sum++;
        prev = cnt;
    }
    
    cout << sum << '\n';
    return 0;
}