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

Ex Input:
Who was British Prime Minister from 1922-23, shortly before he died?

Ex Output:
prime minister of the united kingdom


Ex Input:
Which is the only Avril Lavigne song to have reached No.1 in the US Billboard Chart?

Ex Output:
avril lavigne


Ex Input:
Who wrote the 1938 ballet Billy the Kid?

Ex Output:

billy the kid