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

Example Input: Where is David Cameron's Oxfordshire constituency?
Example Output: david cameron

Example Input: Who stars in the TV series Californication?
Example Output: californication

Example Input: Which actor was a Dad's Army regular and also appeared in the film 'Ben Hur'?
Example Output:
dad's army