#include <bits/stdc++.h>
#define rep(i,n) for(int i = 0; i < (n); i++)
using namespace std;
typedef long long ll;

int main(){
    cin.tie(0);
    ios::sync_with_stdio(0);
    
    int N,M; cin >> N >> M;
    vector<pair<int,int>> seg(M);
    for(auto &[a, b] : seg) cin >> a >> b;
    sort(seg.begin(), seg.end(), [](pair<int,int> I, pair<int,int> J) {
        if(I.second == J.second) return I.first < J.first;
        return I.second < J.second;
    });

    int LAST = -1e9, cnt = 0;
    for(auto [a, b] : seg) {
        if(LAST <= a) {
            cnt++;
            LAST = b;
        }
    }

    cout << 2 * (N - 1) - cnt << endl;
}