#include <bits/stdc++.h>
using namespace std;
typedef unsigned long long ull;
const int max_ = 4e5 + 10;
vector<ull> phi(max_, 0);
vector<ull> primes;
void getPhi();
int main() {
    int n;
    cin >> n;
    getPhi();
    ull ans = 0;
    for (int i = 1; i <= n; ++i) {
        ans += phi.at(i);
    }
    cout << ans * 6;
    return 0;
}

void getPhi() {
    phi.at(1) = 1;
    for (int i = 2; i < max_; i++) {
        if (phi.at(i) == 0) {
            primes.push_back(i);
            phi.at(i) = i - 1;
        }
        for (int j = 0; j < primes.size() && primes.at(j) * i < max_; ++j) {
            int prime = primes.at(j);
            if (i % prime == 0) {
                phi.at(i * prime) = phi.at(i) * prime;
                break;
            } else {
                phi.at(i * prime) = phi.at(i) * (prime - 1);
            }
        }
    }
}