#include<stdio.h>
#include<string.h>
#define Nmax 1000001
int a[Nmax];
long n;
int main()
{
long fr=0,i,k,j;
freopen("fractii.in","r",stdin);
freopen("fractii.out","w",stdout);
scanf("%ld",&n);
long l;
fr=2*n-1;
for(i=2;i<=n;i++)
   {
   for(j=2;j<=n;j++)
      {
      if(i%j==0 && a[j]==0)
	 for(k=1,l=j;l<=n;k++)
	      {
	      a[l]=1;
	      l=j*k;
	      }
      else
       if(a[j]==0)
		fr++;
      }
  memset(a+1,0,sizeof(int)*(n+1));
   }
printf("%ld\n",fr);
return 0;
}