Generate a topic word for the given sentence. A topic word is usually the name of a person, place, animal, concept or object the sentence is focusing on.

Ex Input:
ernest evans (born october 3, 1941) better known as chubby checker, is a pop singer from the united states.

Ex Output:
chubby checker

Ex Input:
a group of his hostages nicknamed him "jihadi john" since he was part of a four-person terrorist cell with british accents whom they called "the beatles".

Ex Output:
jihadi john

Ex Input:
"like father, like clown" is the sixth episode of the simpsons third season.

Ex Output:
like father, like clown