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

Example Input: Which was the title of the 7th and final book in the Chronicles of Narnia by C.S. Lewis?
Example Output: the chronicles of narnia

Example Input: Which engineer built the Menai Suspension Bridge and the Caledonian Canal?
Example Output: menai suspension bridge

Example Input: Who invented the aqualung diving apparatus?
Example Output:
aqua-lung