Given a factoid/trivia type question, generate the topic of the question. The topic is the entity the question talks about.

Input: Consider Input: The Battle of Antietam was fought during which war?

Output: battle of antietam


Input: Consider Input: Of all the actors who played Doctor Who in the TV series of the same name, who appeared in the most episodes?

Output: doctor who


Input: Consider Input: Which Verdi opera opens with a banquet in the palace of the Duke of Mantua?


Output: duke of mantua