instruction:
In this task, you're given an open-domain question. Your task is to provide an answer to the given question. There is only one unique answer for each question. Your answer should be short, and refer to an entity, date, number, etc. Do not put your answer in the context of a sentence.
question:
Who played keyboard on the beatles rooftop concert?
answer:
Billy Preston


question:
When did the civil war end in sierra leone?
answer:
18 January 2002


question:
What marvel movie is after iron man 3?
answer:

Thor: The Dark World