/***************************************************************************
 *   Copyright (C) 2007 by Nistor Andrei   *
 *   [email protected]   *
 *                                                                         *
 *   This program is free software; you can redistribute it and/or modify  *
 *   it under the terms of the GNU General Public License as published by  *
 *   the Free Software Foundation; either version 2 of the License, or     *
 *   (at your option) any later version.                                   *
 *                                                                         *
 *   This program is distributed in the hope that it will be useful,       *
 *   but WITHOUT ANY WARRANTY; without even the implied warranty of        *
 *   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the         *
 *   GNU General Public License for more details.                          *
 *                                                                         *
 *   You should have received a copy of the GNU General Public License     *
 *   along with this program; if not, write to the                         *
 *   Free Software Foundation, Inc.,                                       *
 *   59 Temple Place - Suite 330, Boston, MA  02111-1307, USA.             *
 ***************************************************************************/

#include <fstream>
#include <iostream>

using namespace std;

int N;
unsigned long long k = 1;

void citire() {
    fstream in ( "fractii.in", ios::in );

    in >> N;

    in.close();
}

void tipar() {
    fstream out ( "fractii.out", ios::out );

    out << k;
    out.close();
}

unsigned long phi ( unsigned long n ) {
    unsigned long phi = 1, p;

    for ( p = 2; p * p <= n; p += 2 ) {
        if ( n % p == 0 ) {
            phi *= p - 1;
            n /= p;

            while ( n % p == 0 ) {
                phi *= p;
                n /= p;
            }
        }

        if ( p == 2 )
            p--;
    }

    return ( n == 1 ) ? phi : phi * ( n - 1 );
}

int main ( int argc, char *argv[] ) {
    citire();
	long int i;

    for ( i = 2; i <= N; ++i )
	    k+=2*phi(i);

        tipar();

    return 0;
}