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.

Example Input: lee soo-young (born lee ji-yeon april 12, 1979) is a korean ballad singer.
Example Output: lee soo-young

Example Input: monosemy is when the words in a language each have only one meaning.
Example Output: monosemy

Example Input: solitary confinement is a punishment or special form of imprisonment.
Example Output:
solitary confinement