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 saint petersburg stadium (russian: Стадион Санкт-Петербург; also called the krestovsky stadium or zenit arena) is an association football stadium in saint petersburg, russia.

Ex Output:
saint petersburg stadium


Ex Input:
douglas lawrence "doug" osowski (born january 1, 1969) mostly known as mr. lawrence or doug lawrence is an american voice, actor, comedian, writer, storyboard artist, animator, and director.

Ex Output:
mr. lawrence


Ex Input:
helsinki is the capital city of finland.

Ex Output:

helsinki