#include <iostream>
#include <fstream>

using namespace std;
ifstream in("fractii.in");
ofstream out("fractii.out");

int phi(int n)
{
    int r = n , d = 2;
    while(n > 1)
    {
        if(n % d == 0)
        {
            r = r / d * (d - 1);
            while(n % d == 0)
                n /= d;
        }
        d ++;
        if(d * d > n)
            d = n;
    }
    return r;
}
int main()
{
	int N;
	in >> N;
	int n_max = N;
    for(int i=2;i<=N;i++)
    {
        n_max += 1 + (phi(i)-1)*2;
    }
	out << n_max;
	return 0;
}