#include <iostream>
#include <fstream>
using namespace std;
ifstream f("fractii.in");
ofstream g("fractii.out");

int Euler[1000001];


int main()
{
    int N;
    long long sum = 0;
    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] = Euler[j] / i * (i - 1);
        sum += Euler[i];
    }
    g << 2 * sum + 1;
    return 0;
}