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 is the only Avril Lavigne song to have reached No.1 in the US Billboard Chart?

Answer: avril lavigne


Question: Who choreographed the ballets Swan Lake and Don Quixote, among others?

Answer: don quixote


Question: Deluded by a legend, Francisco Orellana and Gonzalo Pizarro departed from Ecuador in 1541 in a disastrous expedition towards the Amazon Basin; they did not find any gold or lost cities but Orellana became the first person to navigate the entire Amazon River. What were they seeking?

Answer:
amazon