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RIO DE JANEIRO, BRAZIL - AUGUST 06: (L-R) Madeline Groves of Australia, Xinyi Chen of China and Dana Vollmer of the United States compete in heat four of the Women's 100m Butterfly on Day 1 of the Rio 2016 Olympic Games at the Olympic Aquatics Stadium on August 6, 2016 in Rio de Janeiro, Brazil. (Photo by Al Bello/Getty Images)

RIO DE JANEIRO, BRAZIL - AUGUST 06:  (L-R) Madeline Groves of Australia, Xinyi Chen of China and Dana Vollmer of the United States compete in heat four of the Women's 100m Butterfly on Day 1 of the Rio 2016 Olympic Games at the Olympic Aquatics Stadium on August 6, 2016 in Rio de Janeiro, Brazil.  (Photo by Al Bello/Getty Images)