// nemesGyak000.cpp : This file contains the 'main' function. Program execution begins and ends there.
//

#include <iostream>
#include <vector>
#include <algorithm>
using namespace std;

int main()
{
    int length, q;
    cin >> length >> q;
    vector<pair<int, int>> times;
    for (size_t i = 0; i < q; i++)
    {
        int p, n;
        cin >> p >> n;
        times.push_back({p,1});
        times.push_back({n,-1 });
    }
    sort(times.begin(), times.end());
    int Index = 1;
    int SUM = 0;
    int rn = 0;
    bool Switch = true;
    if (times[0].first != 1) rn++;
    for (size_t i = 0; i < times.size(); i++)
    {
        SUM += times[i].second;
        if (times[i].first != Index) {
            Index = times[i].first;
            if (Switch && SUM == 0 && times[i].first!=length) {
                rn++;
                Switch = false;
            }
            if (SUM != 0) {
                Switch = true;
            }
        }
    }
    cout << rn;
}

// Run program: Ctrl + F5 or Debug > Start Without Debugging menu
// Debug program: F5 or Debug > Start Debugging menu

// Tips for Getting Started: 
//   1. Use the Solution Explorer window to add/manage files
//   2. Use the Team Explorer window to connect to source control
//   3. Use the Output window to see build output and other messages
//   4. Use the Error List window to view errors
//   5. Go to Project > Add New Item to create new code files, or Project > Add Existing Item to add existing code files to the project
//   6. In the future, to open this project again, go to File > Open > Project and select the .sln file