#include <fstream>

std::ifstream in("fractii.in");
std::ofstream out("fractii.out");

int64_t sieve[1000001], sievetot[1000001];

int main() {
    int64_t x;
    in >> x;
    for (int i = 2; i <= x; i++) sievetot[i] = i;

    for (int i = 2; i <= x; i++) {
        if (sieve[i]) continue;
        for (int j = 2 * i; j <= x; j += i) sieve[j] = 1;
        for (int j = i; j <= x; j += i) {
            sievetot[j] *= i - 1;
            sievetot[j] /= i;
        }
    }

    int64_t answer = 1;
    for (int64_t i = 2; i <= x; i++) answer += 2 * sievetot[i];

    out << answer;
}