#include <stdio.h>
#include <stdlib.h>


int main(int argc, char const *argv[]) {

  FILE *f;
  int i,j,n;
  f = fopen("fractii.in","r");
  fscanf(f,"%d",&n);
  long long v[1000005];
  for(i=1;i<=n;i++)
    v[i] = i;
  for(i=2;i<=n;i++)
  {
    if(v[i]==i)
    {
      for(j = i; j <= n; j += i) {
             v[j] /= i;
             v[j] *= (i-1);
         }
    }
  }

  long long sum=0;
  for(i=1;i<=n;i++)
    sum += v[i];
  fclose(f);

  f = fopen("fractii.out","w");
  fprintf(f,"%lld\n",2*sum-1);

  return 0;
}