#include <fstream>

using namespace std;
ifstream cin("fractii.in");
ofstream cout("fractii.out");
long long n, phi[1000001], sum;
int main() {
	ios_base::sync_with_stdio(false);
	cin.tie(nullptr);
	cin >> n;
    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;
            }
        }
    }
    for (int i = 2; i <= n; i++)
        sum += phi[i];
    cout << 2 * sum + 1;
	return 0;
}