Runners gather at the start line for the annual “Santa Speedo Run”, a charity race through the streets of the Back Bay neighborhood of Boston. (Photo by Gretchen Ertl/Reuters)

Girls practice sit-ups during gymnastics lessons at the Shanghai Yangpu Youth Amateur Athletic School in Shanghai, China, on May 4, 2016. China's sports system has been enormously successful since the country returned to the Olympic fold in 1980, culminating with the host nation topping the medals' table at the 2008 Beijing Olympics. And yet, with the Rio de Janeiro Games less than three months away, the system is beginning to break down due to the shifting demographics of a more prosperous nation. (Photo by Aly Song/Reuters)

World War II veterans danced during Victory Day celebrations in Minsk, Belarus, Thursday, May 9, 2013. Belarus and other former Soviet countries celebrated the 1945 victory over Nazi Germany on Thursday. (Photo by Viktor Drachev/AFP Photo)

People pour wine at each other during the traditional “Battle of Wine” held as part of the Haro Wine Festival in the La Rioja region in Haro, Spain, 29 June 2016. Every year on 29 June inhabitants and tourists celebrate San Pedro's day by trowing at each other thousands of liters of Riojan wine. (Photo by Abel Alonso/EPA)

Students celebrate their A-level results at King Edward VI High School for Girls in Birmingham, England on August 18, 2016. The proportion of top grades achieved by A-level students across the UK has fallen for a fifth year in a row, and girls have caught up with boys in attaining A* grades. (Photo by Joe Giddens/PA Wire)

The Boeoegg, a giant symbolic snowman made of wadding and and filled with firecrackers burns on top of a bonfire in Sechselaeuten square on April 24, 2017 in Zurich. When the bells of the Saint Peter's church chime six o'clock, the bonfire under the snowman is set in fire and the guildsmen wearing historical costumes ride around the bonfire. The faster the head of the snowman explods the warmer and more beautiful the summer will be. (Photo by Michael Buholzer/AFP Photo)

Russian servicewomen march at Red Square during the Victory Day military parade in Moscow on May 9, 2017. Russia marks the 72nd anniversary of the Soviet Union's victory over Nazi Germany in World War Two. (Photo by Kirill Kudryavtsev/AFP Photo)

A reveller takes part in the Gay Pride Parade in San Salvador, on June 24, 2017. (Photo by Marvin Recinos/AFP Photo)