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

Ex Input:
Which river begins in the Rocky Mountains in south-west Colorado, crosses New Mexico and forms the border between Mexico and the USA before reaching the Gulf of Mexico?

Ex Output:
new mexico


Ex Input:
Which British TV star and disc jockey said `It`s not affected my work - how healthy do you have to be to play Da Do Ron Ron` in 1992 after confirming he had AIDS?

Ex Output:
hiv/aids


Ex Input:
Who was the first actor to star as Batman?

Ex Output:

batman