#include <bits/stdc++.h>
using namespace std;
const int maxn = 1e2 + 5;
const double eps = 1e-7;
const long long mod = 1e9 + 7;
const int N = 100000 + 10;
long long ans;
int n;
void init() {
  for (int i = 2; i <= n; ++i) {
    int cnt = 2;
    for (int j = i + i; j <= n; j += i) {
      ans += (long long)cnt * 4;
      ++cnt;
    }
  }
}
int main() {
  scanf("%d", &n);
  ans = 0;
  init();
  printf("%lld\n", ans);
  return 0;
}
