#include <iostream>
#include <algorithm>
#include <iomanip>
#include <vector>
#include <queue>
#include <set>
#include <map>
#include <tuple>
#include <cmath>
#include <numeric>
#include <functional>
#include <cassert>

#define debug_value(x) cerr << "line" << __LINE__ << ":<" << __func__ << ">:" << #x << "=" << x << endl;
#define debug(x) cerr << "line" << __LINE__ << ":<" << __func__ << ">:" << x << endl;

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; }

using namespace std;
typedef long long ll;
using P = pair<int, int>;

int main(){
    ios::sync_with_stdio(false);
    cin.tie(0);
    cout << setprecision(10) << fixed;
    int n, m; cin >> n >> m;
    vector<P> p(m);
    for(int i = 0; i < m; i++){
        int l, r; cin >> l >> r;
        p[i] = P(l, r);
    }
    sort(p.begin(), p.end());
    priority_queue<int, vector<int>, greater<int>> que;
    int ans = n;
    for(auto [l, r]: p){
        if(!que.empty()){
            if(que.top() < l){
                ans--;
                while(!que.empty()) que.pop();
            }
        }
        que.push(r);
    }
    if(!que.empty()) ans--;
    cout << ans << endl;
}