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: the occipital lobe is the back part of a mammal's brain.

Output: occipital lobe


Input: Consider Input: "the raven" is a narrative poem by american writer edgar allan poe, first published in january 1845.

Output: the raven


Input: Consider Input: cerebral œdema (or cerebral edema) is a build-up of extra fluid in the brain.


Output: cerebral edema