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

int main()
{
    int n, m; cin >> n >> m;
    vector<int> A(n+1,0);
    for(int i = 0; i < m; i++)
    {
        int start, finish; cin >> start >> finish;
        A[start]++;
        A[finish]--;
    }
    for(int i = 2; i <= n; i++){
        A[i] += A[i-1];
    }
    bool start = false;
    int ans = 0;
    for(int i = 1; i <= n; i++)
    {
        if(!start && A[i] == 0) start = true;
        else if(start && A[i] != 0){
            ans++;
            start = false;
        }
    }
    if(start) ans++;
    cout << ans << "\n";

    return 0;
}