#include <stdio.h>

FILE *f,*g;
long i,j,n,npedoi,temp;
char a[1000000];
long long contor;

int main()
{
  f=fopen("fractii.in","r");
  g=fopen("fractii.out","w");
  fscanf(f,"%ld\n",&n);
	contor=n*n-n;
  npedoi=n/2;
  if(n%2==1)
    npedoi++;
	for(i=2;i<=npedoi;i++)
	if(a[i]!=1)
	  {
		  temp=0;
	    for(j=2;i*j<=n;j++)
			  {
		      contor-=2;
					temp++;
					a[i*j]=1;
				}
			contor-=temp*(temp-1);
		}
  fprintf(g,"%lld\n",contor);
  fclose(f);   fclose(g);
  return 0;
}