Sjinkie Knegt of Netherlands, left, and Park Se-Yeong of South Korea crash out as they compete in a men's 1500m short track speedskating final at the Iceberg Skating Palace during the 2014 Winter Olympics, Monday, February 10, 2014, in Sochi, Russia. (Photo by Bernat Armangue/AP Photo)

Jennifer Oeser of Germany competes in the Women's Heptathlon Long Jump on Day 8 of the Rio 2016 Olympic Games at the Olympic Stadium on August 13, 2016 in Rio de Janeiro, Brazil. (Photo by Alexander Hassenstein/Getty Images)

Puerto Rico's Grace Claxton warms up before competing in the Women's 400m Hurdles Round 1 during the athletics event at the Rio 2016 Olympic Games at the Olympic Stadium in Rio de Janeiro on August 15, 2016. (Photo by Jewel Samad/AFP Photo)

An Israeli boy swims next to sheep belonging to a Palestinian farmer in the West Bank village of Al-Auja in the Jordan Valley on April 8, 2015 during the Jewish Passover holiday. Thousands of Israelis spent the day outdoors, picnicking and touring the country during the eight-day Passover holiday, which commemorates the Israelites' exodus from Egypt some 3,500 years ago. (Photo by Menahem Kahana/AFP Photo)

Robot couple Xiaolan (L) and Xiaotao carry trays of food at a restaurant in Jinhua, Zhejiang province, China, May 18, 2015. The restaurant, which opened on Monday, has two robots delivering food for customers. The robots were designed as a couple, Xiaolan and Xiaotao, according to local media. (Photo by Reuters/Stringer)

A child walks to an installation made from fallen leaves by college students, in shape of a sofa, to call for people's attention to environment protection, in Hangzhou, Zhejiang province, China, December 6, 2016. (Photo by Reuters/China Daily)

Dancers perform during the Opening Ceremony of the Rio 2016 Olympic Games at Maracana Stadium on August 5, 2016 in Rio de Janeiro, Brazil. (Photo by Jamie Squire/Getty Images)

A reveller takes part in an annual block party known as “Cordao de Prata Preta”, one of the many carnival parties to take place in the neighbourhoods of Rio de Janeiro, February 6, 2016. (Photo by Pilar Olivares/Reuters)