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.

Input: Consider Input: a black powder rocket motor pushes a model rocket using black powder.

Output: black powder rocket motor

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

Output: lee soo-young

Input: Consider Input: giovanni berlinguer (]), cavaliere di gran croce omri, (9 july 1924 6 april 2015) was an italian politician and professor of social medicine.
Output: giovanni berlinguer