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

Example Input: The bells were ringing for Chuck Berry when this song made it to No1. His first and only British No. 1. What song?
Example Output: chuck berry

Example Input: Which team lost the 2009 Superbowl to the Pittsburgh Steelers?
Example Output: super bowl xliii

Example Input: Which composer wrote the music for the ballet 'Mother Goose' in 1910?
Example Output:
mother goose