#include <iostream>
#include <vector>
#include <string>
#include <algorithm>
#include <cmath>
#include <tuple>
#include <bitset>

#define rep(i,n) for(i=0; i<n; ++i)
#define inc_rep(i,a,n) for(i=a; i<n; ++i)
#define dec_rep(i,n,a) for(i=n; i>=a; --i)
#define in(a) cin >> a
#define out(a,b) cout << a << b
#define print_vec(v) for(auto it=v.begin();it!=v.end();++it)cout<<*it <<" ";cout<<endl
#define print_vec2d(v) for(int i=0;i<v.size();++i){for(int j=0;j<v[i].size();++j)cout<<v[i][j]<<" ";cout<<endl;}cout<<endl
using namespace std;
using lint = long long;

lint ind(lint indx, vector<pair<lint,lint> > v){
    lint left=v[indx].first, right=v[indx].second, i;
    inc_rep(i,indx+1,v.size()){
        if(left<=v[i].first&&v[i].second<=right) return ind(i,v);
    }
    return indx;
}

int main(void){
    lint i, j, k, cnt=0, x, y;
    lint p, q, n, m;
    in(n); in(m);
    vector<pair<lint,lint> > v;
    rep(i,m){
        in(p); in(q);
        v.push_back(make_pair(p,q));
    }
    sort(v.begin(),v.end());
    cnt=(n-1)*2; x=0;
    rep(i,m){
        i=ind(i,v);
        x++;
    }
    out(cnt-x,endl);


    return 0;
}