#include<iostream>
#include<fstream>

using namespace std;

const int Nmax = 1000001;
long long A[Nmax];

int main() {
	ifstream f("fractii.in");
	ofstream g("fractii.out");
	long N;
	long long nr = 1;
	f >> N;
	for ( int i = 2; i <= N; i ++ ) {
		A[i] = i - 1;
	}
	for ( int i = 2; i <= N; i ++ ) {
		nr += 2LL * A[i];
		for ( int j = 2 * i; j <= N; j += i ) {
			A[j] -= A[i];
		}
	}
	g << nr;
	f.close();
	g.close();
	return 0;
}