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

using ll = long long;
using pll = pair<ll,ll>;
using vll = vector<ll>;
using vi = vector<int>;
using pi = pair<int, int>;
using vpi = vector<pair<int, int>>;
using vai = vector<array<int, 3>>;

#define x first
#define y second
#define all(x) x.begin(), x.end()

void solve() {
    int n, k; cin >> n >> k;
    vi diff(n);
    for (int i = 0; i < k; i++) {
        int a, b; cin >> a >> b;
        diff[a-1]++;
        diff[b-1]--;
    }
    int ans = 0, sum = 0;
    bool elozo = false;
    for (int i = 0; i < n-1; i++) {
        sum += diff[i];
        if (sum == 0) {
            if (!elozo) {
                ans++;
                elozo = true;
            }
        } else {
            elozo = false;
        }
    } cout << ans;
}

int main() {
	ios::sync_with_stdio(0);
    cin.tie(0);

    int t=1;
    //cin >> t;
    while (t--) {
        solve();
    }
}