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

Ex Input:
What is the largest country in Africa?

Ex Output:
africa


Ex Input:
Which Chuck Berry song is performed by Marty McFly at the end of the film Back to the Future?

Ex Output:
back to the future


Ex Input:
Which member of the cast of Dad's Army was born in Hayfield in 1915?

Ex Output:

dad's army