#include<stdio.h>
int n,a[2000000],i,j,nr,d;
long long suma=0;
int main()
{
	freopen("fractii.in","r",stdin);
	freopen("fractii.out","w",stdout);
	scanf("%d",&n);
	for(i=1;i<=n;i++)
		   a[i]=i;
suma=n;	
	for(i=2;i<=n;i++)
	   {
		   if(a[i]!=0)
		     {
				 for(j=i*2;j<=n;j+=i)
			         a[j]=0;
				 d=(n-n/i);
				suma+=d;
		       }
		   else
		   {
			   for(j=2;j<i;j++)
			      {
					  if(a[j]!=0)
				        {
							if(i%j==0)
							 {
								 d=n-n/j;
								 suma+=d;
							  }
					      }
			        }
		   }
         }
printf("%d",suma);
return 0;}