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

Example Input: The film The Curious Case of Benjamin Button, starring Brad Pitt, is based on a short story by whom?
Example Output: the curious case of benjamin button

Example Input: What is the main river of Brazil?
Example Output: brazil

Example Input: Now in the Galleria dell'Accademia in Florence, the Renaissance masterpiece, 'The Statue of David is by which sculptor?
Example Output:
david