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

int main() {
    int N,M;
    cin >> N >> M;
    vector<pair<int,int>>tmp(M);
    for(int i = 0; i < M; i++) {
        cin >> tmp[i].second >> tmp[i].first;
    }
    sort(tmp.begin(),tmp.end());
    int mx = 0,sum = 0;
    for(int i = 0; i < M; i++) {
        if(mx >= tmp[i].second) {
            continue;
        }
        mx = tmp[i].first;
        sum++;
    }
    cout << N-sum << endl;
}