#include <iostream>
#include <cstdio>
#include <cstring>
#include <cstdlib>
using namespace std;
#define N 400010
typedef long long LL;
LL phi[N], ans;
bool vis[N];
int tot, n;
int prime[N];
void Euler() {
    phi[1] = 1;
    for (int i = 2; i <= n; i++) {
        if (!vis[i]) {
            prime[tot++] = i;
            phi[i] = i - 1;
        }
        for (int j = 0; j < tot && i * prime[j] <= n; j++) {
            vis[i * prime[j]] = 1;
            if (i % prime[j] == 0) {
                phi[i * prime[j]] = phi[i] * prime[j];
                break;
            } else
                phi[i * prime[j]] = phi[i] * (prime[j] - 1);
        }
    }
}
int main() {
    // freopen("6.in","r",stdin);
    // freopen("6.out","w",stdout);
    scanf("%d", &n);
    Euler();
    for (int i = 1; i <= n; i++) ans += phi[i];
    ans = ans * 6;
    printf("%lld\n", ans);
}