#include <cstdio>

#define MAXN 1000010

int main(){

  freopen("fractii.in", "r", stdin);
  freopen("fractii.out", "w", stdout);

  long long N, i, j, res;
  static int P[MAXN];
  scanf("%lld", &N);

  for(i=2; i<=N; i++)
    P[i]=i-1;

  for(i=2; i<=N; i++)
    for(j=i<<1; j<=N; j+=i)
      P[j]-=P[i];

  res=0;
  for(i=2; i<=N; i++)
    res+=P[i];
  res=(res<<1)+1;

  printf("%lld\n", res);

  return 0;
}