}
    // Guess the size is "halfway between" all duplicates and no duplicates, on a log scale.
    return Math.max(
        ImmutableCollection.Builder.DEFAULT_INITIAL_CAPACITY,
        IntMath.sqrt(inputElementsIncludingAnyDuplicates, RoundingMode.CEILING));
  }

  private static final long serialVersionUID = 0xcafebabe;