#include <bits/stdc++.h>

#define NMax 1000002

using namespace std;

int n, phi[NMax];

int main(){
	ifstream in("fractii.in");
	ofstream out("fractii.out");
	in >> n;
	long long ans = 1;
	phi[1] = 1;

	for(int i = 2; i <= n; i++){
		phi[i] += i - 1;
		ans += phi[i];
		for (int j = i*2; j <= n; j += i){
			phi[j] -= phi[i];
		}
	}

	out << ans * 2 - 1 << '\n';
	return 0;
}