// Source: https://usaco.guide/general/io

#include <bits/stdc++.h>
using ll = long long;
using namespace std;

int main() {
	ll n, m; cin >> n >> m;
    vector<ll> first(m+1, 0);
    vector<ll> second(m+1, 0);
    vector<ll> freq(n+1, 0);
    for (ll i = 1; i <= m; i++){
        cin >> first[i] >> second[i];
        freq[first[i]]++; freq[second[i]]--;
    }
    ll sum = 0, ans = 0;
    for (ll i = 1; i <= n; i++){
        sum += freq[i];
        if (sum == 0) ans++;
    }
    cout << ans-1; // -1 mert állomás párok 
}