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 largest city in Bavaria?
Example Output: bavaria

Example Input: The Byzantine Empire is the term used since the 19th century to describe the Roman Empire of the Middle Ages, centred on its capital, where?
Example Output: byzantine empire

Example Input: Who played Rose Tyler on Doctor Who?
Example Output:
rose tyler