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

int e[1000000];

int main()
{
  int i, j, n;
  long long r;
  FILE *fi=fopen("fractii.in", "r"), *fo=fopen("fractii.out", "w");
  fscanf(fi, "%d", &n);
  for(i=2;i<=n;i++)
    e[i]=i;
  for(i=2;i<=n;i++)
    if(e[i]==i)
      for(j=i;j<=n;j+=i)
        e[j]=e[j]/i*(i-1);
  r=0;
  for(i=2;i<=n;i++)
    r+=e[i];
  fprintf(fo, "%lld", 2*r+1);
  return 0;
}