#include <fstream>

using namespace std;

const int N = 1000000;

int e[N+1];

int main()
{
    ifstream in("fractii.in");
    ofstream out("fractii.out");
    int n;
    in >> n;
    for (int i = 1; i <= n; i++)
    {
        e[i] = i;
    }
    for (int d = 2; d <= n; d++)
    {
        if (e[d] == d)///e[d] nu a fost modificat, deci d este prim
        {
            for (int m = d; m <= n; m += d)
            {
                e[m] = e[m] / d * (d - 1);
            }
        }
    }
    long long s = 0;
    for (int i = 2; i <= n; i++)
    {
        s += 2 * e[i];
    }
    s++;
    out << s;
    in.close();
    out.close();
    return 0;
}