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: louise leakey (born 21 march 1972) is a kenyan paleontologist.
Example Output: louise leakey

Example Input: the wisconsin river is a river in the united states.
Example Output: wisconsin river

Example Input: the southern court (南朝, "nanchō") in japan was a set of four emperors during the nanboku-chō period from 1336 through 1392.
Example Output:
southern court