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:
the river trent is one of the major rivers of england.

Ex Output:
river trent


Ex Input:
nadia sharmeen (bengali: নাদিয়া শারমীন) is a crime reporter from bangladesh, who writes news stories about crime.

Ex Output:
nadia sharmeen


Ex Input:
masahito, prince hitachi (常陸宮正仁親王, hitachi-no-miya masahito shinnō, born 28 november 1935) is a member of the imperial house of japan and the younger brother of emperor akihito.

Ex Output:

masahito, prince hitachi