#include <fstream>

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

int64_t totient(int64_t x) {
    int64_t n = x;
    int64_t p = 2;

    while (x > 1) {
        if (x % p == 0) {
            n *= p - 1;
            n /= p;
            while (x % p == 0) x /= p;
        }
        p++;
    }

    return n;
}

int main() {
    int64_t answer = 1;

    int64_t x;
    in >> x;

    for (int64_t i = 2; i <= x; i++) answer += 2 * totient(i);

    out << answer;
}