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

Example input: Who was the first American President?
Example output: president of the united states
Example explanation: The question talks about the president of the USA.
Q: In which BBC crime drama which ran for six series, did clinical psychologist 'Dr. Tony Hill' work first with 'DI Carol Jordan' and then with 'DI Alex Fielding'?
A:
dr. tony hill