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 Q]: vehari district is a district in the punjab province of pakistan.
[EX A]: vehari district

[EX Q]: a black powder rocket motor pushes a model rocket using black powder.
[EX A]: black powder rocket motor

[EX Q]: vahe was a legendary king of armenia (351 bc–331 bc).
[EX A]:
vahe