#include <stdio.h>
#include <conio.h>
#include <math.h>
int prim(int n)
{
int i,l;
 l=1;
 for (i=2;i<=sqrt(n);i++) if (n % i==0) l=0;
 return l;
    }
int main()
{
int l,n,s,i;
FILE *f=fopen("fractii.in","r");
FILE *g=fopen("fractii.out","w");
     fscanf(f,"%d",&n);
     s=n*n-n+1;
     s=s-(n/2-1)*(n/2-1)-n/2+1;
     for (i=3;i<=n/2;i++)
     {
      if (prim(i)==1) s=s-(n/i-1)*(n/i-1)-n/i+1;   
         }
      fprintf(g,"%d",s);
fclose(f);
fclose(g);
return 0;
    }