#include <fstream>

using namespace std;

ifstream f("fractii.in");
ofstream g("fractii.out");

int N;
int Euler[1000001];
long long int Sol;

int main()
{
    f >> N;
    for(int i = 2; i <= N; i++)
        Euler[i] = i;
    for(int i = 2; i <= N; i++)
    {
        if(Euler[i] == i)
            for(int j = i; j <= N; j += i)
            {
                Euler[j] /= i;
                Euler[j] *= i - 1;
            }
        Sol += Euler[i];
    }
    g << 2 * Sol + 1;
    return 0;
}