Riot police fire tear gas at demonstrators during a protest against fare hikes for city buses in Sao Paulo, Brazil, January 8, 2016. Brazilian riot police on Friday fired tear gas and stun grenades to disperse a violent protest against a rise in public transport fares in the country's largest city, Sao Paulo. (Photo by Nacho Doce/Reuters)

A passenger not wearing pants sits in a subway train during the “No Pants Subway Ride” in Prague, Czech Republic, January 10, 2016. The event is an annual flash mob and occurs in different cities around the world in January, according to its organisers. (Photo by David W. Cerny/Reuters)

Dancers wait backstage during a dress rehearsal for the new “THE ONE Grand Show” at Friedrichstadt-Palast in Berlin, Germany, September 21, 2016. From silver body suits with giant mohawks to revealing fishnet tops with huge feathers, colourful, extravagant costumes take centre stage at a new theatrical show in Berlin. French couturier Jean Paul Gaultier has swapped the Paris runway for the German stage to create some 500 costumes for “THE ONE Grand Show”, an 11-million euro ($12.2 million) production showcasing plenty of singing, dancing and acrobatics. (Photo by Hannibal Hanschke/Reuters)

Harris & Ewing Inc. photographed people, events, and architecture, particularly in Washington, D.C., during the period 1905-1945. Photo: Tests of Curtiss Palne for Army, Single Control. Created by Harris & Ewing. Published in 1912.

Caroline Wozniacki of Denmark serves in her match against Kaia Kanepi of Estonia during day four of the Toray Pan Pacific Open at Ariake Colosseum on September 28, 2011 in Tokyo, Japan. (Photo by Koji Watanabe/Getty Images)

Tourists view Hukou Waterfall on the Yellow River in the frigid winter on December 28, 2023 in Yan'an, Shaanxi Province of China. Freezing winter air has turned Hukou Waterfall into an icy wonderland. (Photo by VCG/VCG via Getty Images)

Protester Lauren Digioia wears police tape during an Occupy Wall Street protest in Union Square on March 19, 2012 in New York City. Protesters affiliated with the movement are gathering in Union Square today following 73 arrests at a six-month anniversary rally at Zuccotti Park over the weekend. (Photo by Mario Tama/Getty Images)

Enthusiasts skate on a frozen fen in sub-zero temperatures on February 11, 2012 in Sutton, England. (Photo by Oli Scarff/Getty Images)