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:
barbara boxer (born november 11, 1940) is an american politician.

Ex Output:
barbara boxer


Ex Input:
arabesque is an artistic decoration.

Ex Output:
arabesque


Ex Input:
korean masks have been used since the 6th century.

Ex Output:

korean mask