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.

[Q]: 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.
[A]: saint petersburg stadium


[Q]: a rearguard is a part of a military force that protects the main force from attack from the rear.
[A]: rearguard


[Q]: murray albert olmstead (september 4, 1926 – november 16, 2015) was a canadian professional ice hockey left winger.
[A]:
bert olmstead