#include <bits/stdc++.h>
int main() {
  int n;
  scanf("%d", &n);
  long long sum = 0;
  int j;
  for (int i = 2; i <= n; i++) {
    int cnt = 0;
    for (j = i + i; j <= n; j += i) sum += (j / i);
  }
  printf("%lld\n", sum * 4);
  return 0;
}
