// UUID: c7f9a9bd-0ed3-4a78-a6da-45b3501a2702
#include <bits/stdc++.h>
using namespace std;

int main() {
	long long n,m;
    cin >> n >> m;

    vector <int> tav (n,0);
    for (long long a,b, i=0; i<m; i++) {
        cin >> a >> b;
        a--; b--;
        tav[a]++; tav[b]--;
    }

    /*long long cnt=0, ans=0;
    bool ures=false;
    for (long long i=0; i<n; i++) {
        cnt+=tav[i];
        if (cnt==0 && !ures) {
            ans++;
            ures=1;
        }
        else if (cnt>0) ures=0;
        
    }*/

    int cnt = 0;
int ans = 0;
bool prev_zero = false;

for (int i = 0; i < n-1; i++) {
    cnt += tav[i];

    bool curr_zero = (cnt == 0);

    if (curr_zero && !prev_zero) {
        ans++;
    }

    prev_zero = curr_zero;
}
    /*
    for (int i = 0; i < n-1; i++) {
        cnt+= tav[i];
        if (cnt == 0) ans++;
    }*/
    cout << ans;
}
//2 0 0 -1 0 -1 0 1 -1 0