// UUID: ad1bd2c9-73c1-4dfd-8a10-b608c885fa5d
#include <bits/stdc++.h>
using namespace std;

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

	vector<int> diffs(n+1, 0);
	for (int i=0;i<m;i++){
		int start, end;
		cin >> start >> end;
		diffs[start]++;
		diffs[end]--;
	}
	// for(int d:diffs){
	// 	cout << d << " ";
	// }
	// cout << "\n";

	int empty_section_count = 0;
	int total = 0;
	for(int i=0;i<=n;i++){
		total += diffs[i];
		if(total==0){ // found the beginning of an empty section
			empty_section_count++;
			while(i<n && total == 0){
				i++;
				total += diffs[i];
			}
		}
	}
	cout << (diffs[1] == 0 ? empty_section_count : empty_section_count -1);
}