#include <fstream>
using namespace std;

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

const int MAX = 1000010;
int a[MAX];
long long N;
long long r;
long long s;

int main()
{
    int i, j;

    fin >> N;
    for ( i = 2; i <= N; i++ )
        a[i] = i;
    for ( i = 2; i <= N; i++ )
        if ( a[i] == i )
        {
            for( j = i; j <= N; j += i )
                a[j] = a[j] / i * ( i - 1 );
        }
    for ( i = 1; i <= N; i++ )
        r += a[i];
    r = r * 2;
    r += 1;

   /* for ( i = 1; i <= N; i++ )
        fout << a[i] << ' ';
    fout << '\n'; */

    fout << r << '\n';

    fin.close();
    fout.close();
    return 0;
}