#include <algorithm>
#include <cmath>
#include <iostream>
#include <map>
#include <numeric>
#include <queue>
#include <set>
#include <vector>
using namespace std;
using ll = long long;
#define rep(i, j, n) for (ll i = j; i < (n); ++i)
#define rrep(i, j, n) for (ll i = (n)-1; j <= i; --i)
#define all(a) a.begin(), a.end()
template <typename T>
std::ostream &operator<<(std::ostream &os, std::vector<T> &a) {
  for (size_t i = 0; i < a.size(); ++i) os << (i > 0 ? " " : "") << a[i];
  return os << '\n';
}
template <typename T>
std::istream &operator>>(std::istream &is, std::vector<T> &a) {
  for (T &x : a) { is >> x; }
  return is;
}

[[maybe_unused]] constexpr long long MOD = 998244353;
// constexpr long long MOD = 1000000007;
[[maybe_unused]] constexpr int INF = 0x3f3f3f3f;
[[maybe_unused]] constexpr long long INFL = 0x3f3f3f3f3f3f3f3fLL;

int main() {
  cin.tie(0)->sync_with_stdio(0);
  int n, m, a, b;
  cin >> n >> m;
  vector<pair<int, int>> ps;
  rep(i, 0, m) {
    cin >> a >> b;
    ps.emplace_back(b, a);
  }
  sort(all(ps));
  int lst = 0;
  int ans = 0;
  for (auto &[b, a] : ps) {
    if (lst <= a) {
      lst = b;
      ++ans;
    }
  }
  cout << 2 * (n - 1) - ans << '\n';
}