#define _CRT_SECURE_NO_WARNINGS
#define _SILENCE_CXX17_C_HEADER_DEPRECATION_WARNING
#include <bits/stdc++.h>
using namespace std;
const int N = 1e5 + 10;
int vis[N];
int main()
{
    for (int i = 2; i < N; i++)
        for (int j = i + i, t = 2; j < N; j += i, t++)
            vis[j] += t;
    int n;
    while (cin >> n)
    {
        long long sum = 0;
        for (int i = 2; i <= n; i++)
            sum += vis[i];
        cout << (sum * 4 + n - 1) << endl;
    }
    return 0;
}