#include <stdio.h>

int n, i, j, rez;
int a[1000000];

int main()
{
  freopen("fractii.in", "r", stdin);
  freopen("fractii.out", "w", stdout);

  scanf("%d", &n);

  rez = n*n;

  
  for (i = 2; i <= n; i++)
    {
      if(a[i] == 0)
	{
	  rez -= (n/i)*(n/i);
	  a[i] = 1;
	  for (j = i*2; j <= n; j += i)
	    {
	      if(a[j])
		{
		  rez++;
		}
	      a[j] = 1;	  
	    }
	}
    }
  
  printf("%d", rez);


  return 0;
}