#include<stdio.h>
#define NMAX 1000005
int k,N,SOL[NMAX];
long long int nr;
void citire()
{
	freopen("fractii.in","r",stdin);
	freopen("fractii.out","w",stdout);
	scanf("%d",&N);
}
void ciur()
{
	int j,i;
	for(i = 1 ; i<= N; i++)
		SOL[i] = i - 1;
	for(i = 2 ; i<= N; i++)
		for(j = 2 ; j*i<= N; j++)
			SOL[i*j]-=SOL[i];
}
void construire()
{
	nr = 1LL;
	for(int i = 2 ; i <= N; i++)
		nr+=(2*SOL[i]);
}
int main()
{
	citire();
	ciur();
	construire();
	printf("%lld",nr);
	return 0;
}