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

Example Input: What is the main river of Brazil?
Example Output: brazil

Example Input: The rivers Axe, Brue, Cary, Parrett, eta, are in which English county?
Example Output: castle cary

Example Input: The detective Albert Campion was created by which author?
Example Output:
albert campion