#include <bits/stdc++.h>
using namespace std;
int main() {
  int n, a, b, i, j, k;
  while (~scanf("%d", &n)) {
    long long int e = 0;
    for (i = 2; i <= n / 2; i++) {
      for (j = i + i; j <= n; j += i) {
        e += 4 * j / i;
      }
    }
    printf("%lld\n", e);
  }
  return 0;
}
