#include<stdio.h>

const long Nmax=1000002;

long long phi[2*Nmax];

long n;

void totient()
{
  for (long i = 1; i <= n; ++i)
      phi[i] = i-1;
  for (long i = 2; i <= n; ++i)
      for (long j = 2*i; j <= n; j += i)
          phi[j] -= phi[i];
}

int main()
{
  freopen("fractii.in","r",stdin);
  freopen("fractii.out","w",stdout);
  long long s=0;
  scanf("%d",&n);
  totient();
  for(int i=2;i<=n;i++)
    s+=phi[i];
  printf("%lld",2*s+1);
  return 0;
}