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:
the river clyde (, ]) is a river in scotland.

Ex Output:
river clyde


Ex Input:
the australian classification board is a government agency in australia that controls censorship and classifications.

Ex Output:
australian classification board


Ex Input:
a fountain is an arrangement, usually made by man; in it, the water from a source is captured in some way.

Ex Output:

fountain