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

Ex Input:
Which film was based on the story The Sentinel by Arthur C Clarke?

Ex Output:
arthur c. clarke


Ex Input:
Which group had UK top ten hits in 1987 with 'Sweet Little Mystery' and 'Angel Eyes'?

Ex Output:
angel eyes


Ex Input:
In 1469, the crowns of the kingdoms of Castile and Aragon were united by the marriage of Isabella and Ferdinand. This was an important event in the history of which country?

Ex Output:

aragon