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

Ex Input:
Joseph Addison and Richard Steele founded (in 1711), and Boris Johnson edited, which British magazine?

Ex Output:
boris johnson

Ex Input:
Carpo and Elara are moons of which planet?

Ex Output:
elara

Ex Input:
Who composed Appalachian Spring (in ballet)?

Ex Output:
appalachian spring