#include <stdio.h>
#include <math.h>
#define nmax 1000000

using namespace std;

int n, nrt, phi[nmax];

void citire ()
{
	scanf("%d",&n);
}

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

int main ()
{
	freopen("fractii.in","r",stdin);
	freopen("fractii.out","w",stdout);
	citire ();
	solve ();
	nrt = 1;
	for (int i = 2; i <= n; i++)
		nrt += phi[i] *2;
	printf("%d",nrt);
}