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

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:
The Bob Dylan songs 'Desolation Row', 'Tombstone Blues' and 'Like A Rolling Stone' featured on which album?

Ex Output:
tombstone blues


Ex Input:
What is the capital of Bavaria?

Ex Output:

bavaria