#include<stdio.h>
#include<alloc.h>

int main()
{
  long n,i,j,*x;
  double s=0;
  FILE *f,*g;
  f=fopen("fractii.in","r");
  g=fopen("fractii.out","w");
  fscanf(f,"%ld",&n);
  x=(long*)malloc(n*sizeof(long));
  for(i=1;i<=n;i++)x[i]=i;
  for(i=2;i<=n;i++)
    if(x[i]==i)
      for(j=i;j<=n;j+=i){x[j]/=i;x[j]*=(i-1);}
  for(i=2;i<=n;i++)s+=x[i];
  s*=2;s++;
  fprintf(g,"%.0lf",s);
  fclose(f);fclose(g);
  return 0;
}