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

Ex Input:
Which actress played Arwen in the trilogy of films?

Ex Output:
arwen

Ex Input:
What style of facial hair was famously worn by American Civil War general Ambrose Burnside?

Ex Output:
ambrose burnside

Ex Input:
What kind of bean is used to make tempeh?

Ex Output:
bean