#include <stdio.h>
#include <stdlib.h>
#define NMAX 1000001

int v[NMAX];
int main() {
  FILE *fin, *fout;
  int n, i, poz;
  long long int s;

  fin = fopen("fractii.in", "r");
  fout = fopen("fractii.out", "w");
  fscanf(fin, "%d", &n);

  for(i = 1; i <= n; i++)
    v[i] = i;
  for(i = 1; i <= n; i++) {
    for(poz = 2 * i; poz <= n; poz += i)
      v[poz] = v[poz] - v[i];
  }

  s = 1;
  for(i = 2; i <= n; i++)
    s += 2 * v[i];

  fclose(fin);

  fprintf(fout, "%lld\n", s);
  fclose(fout);
  return 0;
}