#include <iostream>
#include <fstream>

using namespace std;
const int NMAX = 1e6;

int phi[1 + NMAX];

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

ifstream fin ( "fractii.in" );
ofstream fout ( "fractii.out" );

int main()
{
   int n; fin >> n;
   ciur_phi ();

   long long sum = 0;
   for ( int i = 1; i <= n; i ++ )
      sum += phi[i] * 2;

   fout << sum - 1;
    return 0;
}