#include <fstream>

using namespace std;

const int VMAX = 1e6;

int e[VMAX+1];

long long suma_euler(int n)
{
    for (int i = 2; i <= n; i++)
    {
        e[i] = i;
    }
    for (int i = 2; i <= n; i++)
    {
        if (e[i] == i)///i este prim
        {
            for (int mult = i; mult <= n; mult += i)
            {
                e[mult] = e[mult] / i * (i - 1);
            }
        }
    }
    long long s = 0;
    for (int i = 2; i <= n; i++)
    {
        s += e[i];
    }
    return s;
}

int main()
{
    ifstream in("fractii.in");
    ofstream out("fractii.out");
    int n;
    in >> n;
    out << 1 + 2 * suma_euler(n) << "\n";
    in.close();
    out.close();
    return 0;
}