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

Ex Input:
What was the last silent film in which Chaplin's little tramp appeared?

Ex Output:
chaplin

Ex Input:
Who has taken over the TV role of Doctor Who, from actor David Tennant?

Ex Output:
doctor who

Ex Input:
LeeAnne Rimes and Carrie Underwood are associated with what sort of music?

Ex Output:
carrie underwood