Generate a topic word for the given sentence. A topic word is usually the name of a person, place, animal, concept or object the sentence is focusing on.

Q: jujutsu (, jujutsu) is an ancient japanese martial art.

A: jujutsu
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Q: bobby ryan (born robert shane stevenson; march 17, 1987 in cherry hill, new jersey) is an american professional ice hockey right winger.

A: bobby ryan
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Q: proxima centauri is a red dwarf star that is likely a part of the alpha centauri star system and is the closest star to the sun at a distance of 4.22 ly.

A:
proxima centauri
****