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.

Input: Consider Input: cumulative voting is a system for doing an election.

Output: cumulative voting

Input: Consider Input: the embassy of russia in copenhagen is the embassy of russia to denmark.

Output: embassy of russia in copenhagen

Input: Consider Input: war tax due stamp is a kind of war tax and postage due stamps that was used for mail when the war tax has not been paid by the sender.
Output: war tax due stamp