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:
nelsan ellis (november 30, 1977 july 8, 2017) was an american actor and playwright.

Ex Output:
nelsan ellis

Ex Input:
noel cobb (21 march 1938 2 january 2015) was an american-born british philosopher, psychologist, and author.

Ex Output:
noel cobb

Ex Input:
the long-beaked echidnas make up one of the two genera (genus zaglossus) of echidna.

Ex Output:
long-beaked echidna