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.

Example Input: the viol (rhymes with "mile") is a string instrument that is played with a bow.
Example Output: viol

Example Input: anton rubinstein (born vikhvatinets 28 november 1829; died petershof 20 november 1894) was a russian pianist and composer.
Example Output: anton rubinstein

Example Input: commandos are military soldiers who have been highly trained in combat.
Example Output:
commando