#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; r = (( N - 1 ) * N + 1 );
    for ( i = 2; i <= N / 2; i++ )
        if ( a[i] == 0 )
        {
            s = 2;
            for( j = i * 2; j <= N; j += i )
                a[j] += s, r -= s, s += 2;
        }

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

    fout << r << '\n';

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