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The 25-year-old world champion scored 16 for his routine, with 9.2 for execution and 6.8 for difficulty.
Brazilian Arthur Zanetti, the London 2012 champion, went last and finished with 15.766 and a silver medal.
Russia's Denis Ablyazin, who was only cleared to compete with the rest of his country's gymnasts the day before the Olympics began, won bronze with 15.7.
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Greece's Eleftherios Petrounias won gold on the rings in the Olympic gymnastics in Rio.