#include <iostream>
#include <fstream>

using namespace std;

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

const int N = 1e6;
int phi[N + 1];

int main ( ) {
    
    int n, i, j;
    long long s = 0;
    
    for ( i = 1; i <= N; i++ )
        phi[i] = i;

    for ( i = 2; i <= N; i++ )
        if ( phi[i] == i )
            for ( j = i; j <= N; j = j + i )
                phi[j] = phi[j] / i * ( i - 1 );
    
    fin >> n;
    
    for ( i = 1; i <= n; i++ ) {
        s = s + phi[i];
    }
    
    fout << s * 2 - 1;
    
    return 0;
}