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

Ex Input:
Which British Prime Minister married Clementine Hozier on September 12th 1908?

Ex Output:
clementine churchill

Ex Input:
After Harold McMillan who was Britain's next Prime Minister?

Ex Output:
britain

Ex Input:
Which pop singer is the mother of Blue Ivy Carter?

Ex Output:
blue ivy carter