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:
chogolisa is a 7665 m mountain in the karakoram range, in pakistan.

Ex Output:
chogolisa

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

Ex Output:
black powder rocket motor

Ex Input:
yi i (december 26, 1536-1584) was a korean confucian scholar.

Ex Output:
yi i