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

Ex Input:
What's the name of Doctor Who's home planet ?

Ex Output:
doctor who


Ex Input:
What's missing: Magnum Force, The Enforcer, Sudden Impact, and The Dead Pool?

Ex Output:
sudden impact


Ex Input:
In which Shakespeare play does Banquo's ghost appear?

Ex Output:

banquo