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RIO DE JANEIRO, BRAZIL - AUGUST 08: Michael Phelps of United States celebrates winning the Men's 200m Butterfly and his 20th Olympic Gold medal on Day 4 of the Rio 2016 Olympic Games at the Olympic Aquatics Stadium on August 9, 2016 in Rio de Janeiro, Brazil. (Photo by Ian MacNicol/Getty Images)

RIO DE JANEIRO, BRAZIL - AUGUST 08:  Michael Phelps of United States celebrates winning the Men's 200m Butterfly and his 20th Olympic Gold medal on Day 4 of the Rio 2016 Olympic Games at the Olympic Aquatics Stadium on August 9, 2016 in Rio de Janeiro, Brazil. (Photo by Ian MacNicol/Getty Images)