#include <iostream>
#include <cmath>
#include <fstream>
using namespace std;
ifstream in("fractii.in");
ofstream out("fractii.out");
int f (long long int x) {
	long long int d = 2;
	float p = 1;
	long long int cx = x;
	while (x != 1) {
		if (x % d == 0) {
			p = p * (1.0 - 1.0 / (float)d);
			while (x % d == 0) {
				x /= d;
			}
		}
		d++;
	}

	return p * cx;
}

int main()
{
	long long int n, nr = 0;
	in >> n;
	for (int i = 1; i <= n; i++) {
		nr +=(int) 2 * f(i);
	}
	out << nr - 1;

}