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

[Q]: Who directed the film `Back To The Future`?
[A]: back to the future


[Q]: In which city were the 2002 Winter Olympic Games held?
[A]: 2002 winter olympics


[Q]: Brasilia is the capital but which city in Brazil has the largest population?
[A]:
brazil