Aerobatic aircrafts fly during a performance at the Airshow Zhengzhou 2017 in Zhengzhou, capital of central China's Henan Province on April 27, 2017. The 5-day air show kicked off in Zhengzhou on Thursday, aiming to build a general aviation gathering center for business and communications. (Photo by Li An/Xinhua via ZUMA Wire)

St Andrews University students skinny dip in the sea as May Day celebrations in St Andrews, Scotland on April 30, 2017. Hundreds of revellers ditched their clothes and bravely jumped into the bitterly cold North Sea. (Photo by Alamy Stock Photos)

The car driven by Scott Dixon, of New Zealand, goes over the top of Jay Howard, of England, in the first turn during the running of the Indianapolis 500 auto race at Indianapolis Motor Speedway, Sunday, May 28, 2017, in Indianapolis. (Photo by Marty Seppala/AP Photo)

A man takes a picture of sea spray as storms hit Cape Town, South Africa, June 7, 2017. (Photo by Mike Hutchings/Reuters)

Jason Garcia poses as The Joker from Batman at the 2015 Comic-Con International in San Diego, California, July 9, 2015. (Photo by Sandy Huffaker/Reuters)

Waura Indians wrestle during this year's “quarup”, a ritual held over several days to honour in death a person of great importance to them, in Xingu National Park, Mato Grosso State, Brazil August 25, 2013. (Photo by Ueslei Marcelino/Reuters)

Shamans perform a ritual of predictions for the upcoming US election with posters of presidential candidates Donald Trump and Hilary Clinton at the Agua Dulce beach in Lima on November 7, 2016. Hillary Clinton and Donald Trump launched into the frenzied final day of their historic fight for the White House Monday, with blow-out rallies in the handful of swing states that will decide who leads the United States. (Photo by Ernesto Benavides/AFP Photo)

A street actor dressed as a devil frightens children in downtown Prague in Prague, Czech Republic, Monday, December 5, 2016. On the eve of St. Nicholas, Czechs traditionally celebrate by dressing up as Devils, Angels and St. Nicholas, and visiting children in their homes handing out small presents, coal, potatoes or other gifts. (Photo by Petr David Josek/AP Photo)