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:
island of the blue dolphins is an american book written for children by scott o'dell.

Ex Output:
island of the blue dolphins


Ex Input:
a video projector takes a video signal and projects the corresponding image on a screen using a lens system.

Ex Output:
video projector


Ex Input:
marlon jackson (born march 12, 1957) is an american singer and musician.

Ex Output:

marlon jackson