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

Ex Output:
black powder rocket motor


Ex Input:
glenn branca (october 6, 1948 – may 13, 2018) was an american avant-garde composer and guitarist.

Ex Output:
glenn branca


Ex Input:
chumbawamba were a british alternative rock group.

Ex Output:

chumbawamba