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

Example Input: Who was British Prime Minister from 1922-23, shortly before he died?
Example Output: prime minister of the united kingdom

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

Example Input: In which constellation is the star Betelgeuse?
Example Output:
betelgeuse