#include <fstream>
#include <vector>

using namespace std;

ifstream cin("fractii.in");
ofstream cout("fractii.out");

vector<int> phi;

void phi_1_n(int n) {
    phi.resize(n + 2);
    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;
            }
        }
    }
}

int main() {
    int n;
    cin >> n;
    phi_1_n(n);
    long long sum = 0;
    for (int i = 1 ; i <= n ; ++i) {
        sum += 2 * phi[i];
    }
    cout << sum - 1;
    return 0;
}