#include <fstream>
int N;
long S = 1;


int phi(int n)
{
    int result = n, p = 2;
    while (p * p <= n)
    {
        if (n % p == 0)
        {
            result -= result / p;
        }
        while (n % p == 0)
        {
            n /= p;
        }
        ++p;
    }

    if (n > 1)
    {
        result -= result / n;
    }
    return result;
}


int main()
{
    std::ifstream fisierIN("fractii.in");
    fisierIN >> N;

    for (int k = 2; k <= N; ++k)
    {
        S += 2 * phi(k);
    }

    std::ofstream fisierOUT("fractii.out");
    fisierOUT << S;
}