#include<stdio.h>

long n,i,j;
long long a[1000001];
long long b;

int main()
{
	freopen("fractii.in","r",stdin);
	freopen("fractii.out","w",stdout);
	b=1;
	scanf("%ld",&n);
	for(i=2;i<=n;i++)
	  {
	  a[i-2]=(long long)(a[i-2]+i-1);
	  for(j=2*i;j<=n;j+=i)
            {
    		a[j-2]=(long long)(a[j-2]-a[i-2]);
            }
	  b=(long long)(b+2*a[i-2]);
	  }
	 printf("%lld\n",b);
	 return 0;
}