Brazilian natives of the Pareci tribe play head football with a hand-made ball for a demonstration, during the first day of the International Games of Indigenous Peoples, in Cuiaba, state of Mato Grosso, on November 10, 2013. 1500 natives from 49 Brazilian ethnic groups and from another 17 countries are gathering in Cuiaba until November 16 to compete in some 30 athletic disciplines, many of their own. (Photo by Christophe Simon/AFP Photo)

Members of China Disabled Peoples Performing Art Troupe perform “Thousand-arm Goddess of Mercy” during a show on March 12, 2005 in Guangzhou of Guangdong Province, China. China Disabled Peoples Performing Art Troupe was established in 1987. It is an amateur mass art troupe composed of visually impaired, audibly impaired and physically and mentally challenged people. In the past nearly two decades, the troupe has visited more than 30 countries and regions, winning the hearts of audiences all over the world by their solid background of Chinese Culture and their colourful national charm. (Photo by China Photos/Getty Images)

Hostesses pose for photos with a police officer on the motorized vehicle during the third plenary meeting of the 11th National Committee of the Chinese People's Political Consultative Conference (CPPCC) at The Great Hall Of The People on March 10, 2012 in Beijing, China. (Photo by Feng Li/Getty Images)

Afghan air force 2nd Lt. Niloofar Rhmani walks the flight line at Shindand Air Base, Afghanistan, prior to her graduation from undergraduate pilot training, on May 13, 2013. Rhmani made history on May 14, when she became the first female to successfully complete undergraduate pilot training and earn the status of pilot in more than 30 years. She will continue her service as she joins the Kabul Air Wing as a Cessna 208 pilot. (Photo by Senior Airman Scott Saldukas/USAF)

Nazi dictator Adolf Hitler greets supporters at a May Day gathering in the Olympic Stadium, Berlin. (Photo by Keystone). 1st May 1938

Students from the University of St Andrews jump into The North Sea, as a good luck tradition before exams start on the East Sands in St Andrews, Fife, Scotland on May 1, 2018. (Photo by Derek Allan/Alamy Live News)

Fifty years ago, as France exploded in mass protests, words scrawled on the walls of the Sorbonne summed up the revolutionary zeal of the time: “Run free, comrade, we’ve left the old world behind!”. Sexual liberation, artistic creativity and anti-capitalism were the order of the day. For those who were there, it was an unforgettable time. Here: A wounded student is transported by first-aid workers during riots on the Boulevard Saint-Michel, Paris, France on May 6, 1968. (Photo by Gökşin Sipahioğlu/SIPA Press)

A reveller walks through the streets in the early hours during traditional May Day celebrations in Oxford, Britain, May 1, 2015. (Photo by Dylan Martinez/Reuters)