#include <fstream>
#include <math.h>
#define nmax 1000005

using namespace std;

int n;
long long nrt, phi[nmax];

void citire ()
{
	ifstream in("fractii.in");
	in >> n;
}

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

int main ()
{
	citire ();
	solve ();
	nrt = 1;
	for (int i = 2; i <= n; i++)
		nrt += phi[i] *2;
	ofstream out("fractii.out");
	out << nrt;
}