#include <bits/stdc++.h>
using namespace std;
using ll = long long;
#define rep(i, s, e) for (int i = (int)(s); i < (int)(e); ++i)
#define all(a) (a).begin(),(a).end()

int main() {
    cin.tie(nullptr);
    ios_base::sync_with_stdio(false);
    
    int N, M;
    cin >> N >> M;
    vector<pair<int, int>> seg(M);
    rep(i, 0, M) cin >> seg[i].second >> seg[i].first;
    
    sort(all(seg));
    
    int ans = 0;
    int now = 0;
    rep(i, 0, M) {
        if (now < seg[i].second) {
            ++ans;
            now = seg[i].first;
        }
    }
    
    cout << N - ans << '\n';
}