#include <iostream>
#include <vector>
#include <algorithm>
using namespace std;

int N, M;
typedef pair<int,int> pint;

vector<pint> A;
bool cmp(pint a, pint b) { return a.second < b.second; }

int main() {
    cin >> N >> M;
    A.resize(M);
    for (int i = 0; i < M; ++i) cin >> A[i].first >> A[i].second;
    sort(A.begin(), A.end(), cmp);
    int res = 0;
    int endtime = 0;
    for (int i = 0; i < M; ++i) {
        if (A[i].first-1 >= endtime) {
            endtime = A[i].second;
            ++res;
        }
    }
    cout << N-res << endl;
}