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

Let me give you an example: Who was the first American President?
The answer to this example can be: president of the united states
Here is why: The question talks about the president of the USA.

OK. solve this:
Peter Blake, Richard Hamilton, Claes Oldenburg, and Jim Dine were amongst the leading exponents of which 1950's / 60's style of painting?
Answer:

Show your work and conclude with the exact phrasing "Therefore, the final answer is [answer]." where [answer] is just the final number or expression that solves the problem.
user
peter blake