Romanian military doctors and medical students sit on a bus behind steamy windows before the National Day parade in Bucharest, Romania, Thursday, December 1, 2016. Military planes and helicopters flew over the Romanian capital Thursday as thousands turned out to celebrate the national day, marking the date when the country reunified with Transylvania in 1918. (Photo by Vadim Ghirda/AP Photo)

A man dressed as Father Frost, Russian equivalent of Santa Claus, sits by the fire with a reindeer Yakut, marking winter solstice at the Royev Ruchey Park of Flora and Fauna in the Siberian Taiga wood in the suburbs of Krasnoyarsk, Russia, December 21, 2016. (Photo by Ilya Naymushin/Reuters)

People view the sunrise scene at the Bund in Shanghai, east China, January 1, 2017. (Photo by Wang Hechun/Xinhua/Barcroft Images)

South African surfer Andy Marr rides a wave at Dungeons offshore reef in the Atlantic Ocean outside Cape Town, South Africa, 01 September 2016. The big wave surfing season is at its peak with winter swells driven by storms in the South Atlantic breaking on the Cape's outer reefs providing good conditions. Big wave surfers are competing in the 2016 Striped Horse Challenge and Rebel Sessions big wave competitons symultaneously throughout the season. (Photo by Nic Bothma/EPA)

Students exercise in body training at Bishan Vocational Education Center in Chongqing, southwest China, January 13, 2016. These students were trained to be stewardesses of the high-speed train. (Photo by Xie Jie/Xinhua)

A racegoers walks into a rubbish bin following 2016 Melbourne Cup Day at Flemington Racecourse on November 1, 2016 in Melbourne, Australia. (Photo by Scott Barbour/Getty Images)

Model Adriana Lima attends Madonna presents An Evening of Music, Art, Mischief and Performance to benefit Raising Malawi at Faena Forum on December 2, 2016 in Miami Beach, Florida. (Photo by Jeff Kravitz/FilmMagic for Raising Malawi)