#include <bits/stdc++.h>
using namespace std;

#ifdef _RUTHEN
#include "debug.hpp"
#else
#define show(...) true
#endif

using ll = long long;
#define rep(i, n) for (int i = 0; i < (n); i++)
template <class T> using V = vector<T>;

int main() {
    ios::sync_with_stdio(false);
    cin.tie(0);
    int N, M;
    cin >> N >> M;
    V<pair<int, int>> RL(M);
    rep(i, M) cin >> RL[i].second >> RL[i].first;
    sort(RL.begin(), RL.end());
    int ans = 0, rm = 0;
    for (auto [r, l] : RL) {
        if (rm <= l) {
            rm = r;
            ans++;
        }
    }
    ll res = 2 * (N - 1) - ans;
    cout << res << '\n';
    return 0;
}