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

Ex Input:
Chris Martin is the lead singer with which band who had several hits in the 2000s?

Ex Output:
chris martin

Ex Input:
What was the title of Britney Spears' second album (and the single that was released from it)?

Ex Output:
britney spears

Ex Input:
What country used the Drachma as its currency, before switching to the Euro in 2001?

Ex Output:
greek drachma