#include <fstream>

using namespace std;

ifstream fin("fractii.in");
ofstream fout("fractii.out");

int n;
long long sum;
int phi[1000002];

int main()
{
    fin >> n;

    sum = 0;
    for (int i = 1; i <= n; ++i)
        phi[i] = i;
    for (int i = 2; i <= n; ++i)
    {
        if (phi[i] == i)
            for (int j = i; j <= n; j += i)
                phi[j] = (phi[j] / i) * (i - 1);
        sum += 2 * phi[i];
    }

    fout << sum + 1;

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