Given a factoid/trivia type question, generate the topic of the question. The topic is the entity the question talks about.
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Question: Which group had UK top ten hits in 1987 with 'Sweet Little Mystery' and 'Angel Eyes'?

Answer: angel eyes


Question: Who is the only British Prime Minister to serve under 3 monarchs?

Answer: prime minister of the united kingdom


Question: Who played Private Joe Walker in Dad's Army?

Answer:
private walker