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: walter rudolf hess (17 march 1881 12 august 1973) was a swiss physiologist.

Output: walter rudolf hess

Input: Consider Input: a sonata is a piece of music for one instrument or one instrument with another instrument accompanying.

Output: sonata

Input: Consider Input: musa ibrahim is a bangladeshi mountaineer and a journalist.
Output: musa ibrahim