#include<stdio.h>
#define Nmax 500003


FILE *fin=freopen("fractii.in","r",stdin),
     *fout=freopen("fractii.out","w",stdout); 


long n,phi[2*Nmax];

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

int main()
{
  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;
}