#include <map>
#include <set>
#include <ctime>
#include <cmath>
#include <queue>
#include <stack>
#include <vector>
#include <string>
#include <cstring>
#include <cstdio>
#include <cstdlib>
#include <iostream>
#include <algorithm>
#include <functional>
#define spause() system("pause")

using namespace std;
typedef long long llong;
typedef unsigned long long ullong;
typedef pair<int, int> prdd;
typedef map<int, int> mpdd;

const int dinf = 0x7fffffff;
const llong llinf = 0x7fffffffffffffff;
const int p = 998244353;
llong starttime;

int phi[525000];
vector<int> ps;

int n;
llong ans = 0;

void Euler(int rge) {
    phi[1] = 1;
    for (int i = 2; i <= rge; i++) {
        if (phi[i] == 0) {
            phi[i] = i - 1;
            ps.push_back(i);
        }
        for (int j = 0; j < ps.size() && ps.at(j) <= rge / i; j++) {
            if (i % ps.at(j) == 0) {
                phi[i * ps.at(j)] = phi[i] * ps.at(j);
                break;
            } else
                phi[i * ps.at(j)] = phi[i] * (ps.at(j) - 1);
        }
    }
}
// I.	phi(p) = p - 1.
// II.	if : i mod p = 0 -> phi(i * p) = phi(i) * p.
// III. if : i mod p �� 0 -> phi(i * p) = phi(i) * (p-1).

inline llong ngmod(llong a, llong p) { return ((a % p) + p) % p; }

int main() {
    scanf("%d", &n);
    Euler(n);
    for (int i = 1; i <= n; i++) ans += phi[i];
    ans *= 6;
    printf("%lld", ans);

    spause();
    return 0;
}