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

Ex Input:
Who had a hit album with Back to Bedlam in 2005?

Ex Output:
back to bedlam


Ex Input:
Mr Barkis, Edward Murdstone and Tommy Traddles are all characters in which Charles Dickens novel?

Ex Output:
charles dickens


Ex Input:
What is the longest river in Australia?

Ex Output:

australia