#include <fstream>
using namespace std;

const int N = 1e6+5;

ifstream fin ("fractii.in");
ofstream fout ("fractii.out");

int phi[N], n;
long long sol;

int main() {
	fin >> n;
	phi[1] = 1;
	for (int i = 2; i <= n; ++i)
		phi[i] = i - 1;
	for (int i = 2; i * 2 <= n; ++i)
		for (int j = i * 2; j <= n; j += i)
			phi[j] -= phi[i];
	for (int i = 1; i <= n; ++i)
		sol += phi[i];
	sol <<= 1;
	fout << sol-1;
	fcloseall();
}