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

Example Input: Which of the American Idol judges has been there for all 10 seasons?
Example Output: american idol

Example 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?
Example Output: new mexico

Example Input: In which Australian state is one of the southern hemisphere's most remarkable sites, Ayers Rock?
Example Output:
australia