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

Ex Input:
What is the title of the four-episode special of 'Doctor Who', made for the Red Nose Day telethon in the UK, broadcast in March 1999?

Ex Output:
doctor who


Ex Input:
Dora Maar au Chat and The Weeping Woman are both portraits by which artist of his lover?

Ex Output:
dora maar au chat


Ex Input:
What is the title of the first BBC television series to be sold to the Soviet Union?

Ex Output:

bbc