#include <bits/stdc++.h>
const long long INF = 1e18;
using namespace std;
long long ssum(long long multiple) {
  return (multiple * (multiple + 1) / 2 - 1);
}
int main() {
  ios::sync_with_stdio(0);
  cin.tie(0);
  int n;
  cin >> n;
  long long sum = 0;
  for (int i = 2; i <= n; i++) {
    long long multiple = n / i;
    long long ss = 2 * ssum(multiple);
    sum += ss;
  }
  cout << 2 * sum << "\n";
  return 0;
}
