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