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:
nickel creek was an american acoustic musical group.

Ex Output:
nickel creek


Ex Input:
the diplura are a biological order.

Ex Output:
diplura


Ex Input:
the menstrual cycle is a process that uninseminated human women go through about every 28 days.

Ex Output:

menstrual cycle