#include <bits/stdc++.h>
#include <atcoder/all>
using namespace std;
using namespace atcoder;
typedef int64_t lint;
#define rep(i, n) for(int i=0; i<n; i++)
#define repx(i, l, n) for(int i=l; i<n; i++)
#define all(v) v.begin(), v.end()
#define show(x) cout << #x << ": " << x << endl;
#define list(x) cout << #x << ": " << x << "  ";
#define pb push_back
using vi = vector<lint>;
using vvi = vector<vector<lint>>;
template<class T> inline void vin(vector<T>& v) { rep(i, v.size()) cin >> v.at(i); }
template<class T> inline bool chmax(T& a, T b) { if (a < b) { a = b; return 1; } return 0; }
template<class T> inline bool chmin(T& a, T b) { if (a > b) { a = b; return 1; } return 0; }
template<class T> inline void drop(T x) { cout << x << endl; exit(0); }
template<class T> void vout(vector<T> v) { rep(i, v.size()) { cout << v.at(i) << ' '; } cout << endl; }
constexpr lint LINF = LLONG_MAX/2;
using pint = pair<lint, lint>;
using vp = vector<pint>;

int main() {
	lint N, M;
	cin >> N >> M;
	vp v(M);

	lint a=0, b=0, c=-1, x, y, z;
	rep(i, M) {
		cin >> x >> y;
		v[i] = {x-1, -(y-1)};
	}
	sort(all(v));
	rep(i, M) v[i].second *= -1;
	vi w(N, LINF);
	rep(i, M) {
		tie(x, y) = v[i];
		auto l = lower_bound(all(w), y);
		if (chmin(w[l-w.begin()], y)) c = x;
	}
	rep(i, N) {
		if (w[i] != LINF) a++;
		else break;
	}
	std::cout << a << '\n';
}