Given a factoid/trivia type question, generate the topic of the question. The topic is the entity the question talks about.

Input: Consider Input: Of all the actors who played Doctor Who in the TV series of the same name, who appeared in the most episodes?

Output: doctor who


Input: Consider Input: Charon is a moon which orbits which body?

Output: charon


Input: Consider Input: On January 26, 1879, who was granted a patent for r an electric lamp using a carbon filament or strip coiled and connected to platina contact wires?


Output: incandescent light bulb