#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
typedef pair<ll, ll> P;
#define DUMP(x) cout << #x << " = " << (x) << endl;
#define FOR(i, m, n) for (ll i = m; i < n; i++)
#define IFOR(i, m, n) for (ll i = n - 1; i >= m; i--)
#define REP(i, n) FOR(i, 0, n)
#define IREP(i, n) IFOR(i, 0, n)
#define ALL(v) (v).begin(), (v).end()
#define SZ(x) ll(x.size())

int main() {
  ll n, m;
  cin >> n >> m;
  vector<ll> l(m), r(m);
  REP(i, m) { cin >> l[i] >> r[i]; }
  vector<ll> ord(m);
  iota(ALL(ord), 0);
  sort(ALL(ord), [&](ll i, ll j) { return r[i] < r[j]; });
  ll ans = n, p = -1;
  REP(ii, m) {
    ll i = ord[ii];
    ll cl = l[i], cr = r[i];
    if (cl <= p && p <= cr) {
      continue;
    }
    ans--;
    p = cr;
  }
  cout << ans << endl;
}