Given a factoid/trivia type question, generate the topic of the question. The topic is the entity the question talks about.
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Question: Allopurinol is typically prescribed for which illness?

Answer: allopurinol


Question: In which famous film did Michael Caine play a character named Charlie Croker?

Answer: charlie croker


Question: Who directed the film `Back To The Future`?

Answer:
back to the future