#include <fstream>
unsigned N;
unsigned phi[1000001];
long long S = 1;

void init()
{
    for (int i = 1; i <= N; ++i)
    {
        phi[i] = i - 1;
    }
    for (int i = 2; i <= N; ++i)
    {
        for (int j = 2 * i; j <= N; j += i)
        {
            phi[j] -= phi[i];
        }
    }
}


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

    init();
    for (unsigned i = 2; i <= N; ++i)
    {
        S += phi[i] * 2;
    }

    std::ofstream fisierOUT("fractii.out");
    fisierOUT << S;
    fisierOUT.close();
    return 0;
}