Soldiers take part in a drill during a heavy snow in Heihe, Heilongjiang province, February 26, 2014. (Photo by Reuters/China Daily)

Soldiers of People's Liberation Army (PLA) Lanzhou Military Region jump through a burning obstacle during a training session at a military base in Tianshui, Gansu province, China, January 6, 2016. (Photo by Reuters/Stringer)

In this Monday, October 8, 2018 photo, Colombia's BMX freestyle athlete Sebastian Martinez practices at the Urban Park, at the Youth Olympic Games in Buenos Aires, Argentina. (Photo by Ian Walton/OIS/IOC via AP Photo)

Street entertainer and fortune teller “Juana La Cubana” smiles holding a cigar in her mouth as she waits for tourists in Havana, Cuba, Sunday, May 24, 2015. Juana is 72 years old and has worked in the Cathedral square in Old Havana for 28 years. (Photo by Desmond Boylan/AP Photo)

Tourists pose with pigeons in the flooded St. Mark's Square in Venice, on November 7, 2014. The high water, a combination of high tides and a strong Scirocco wind in the Adriatic Sea, stood at 110 centimeters early on November 7. The city has for years been wrestling with the problems posed by the threat of rising sea levels. (Photo by Olivier Morin/AFP Photo)

Riot security forces clash with demonstrators as a motorcycle is set on fire during a protest against Venezuelan President Nicolas Maduro's government in San Cristobal, Venezuela May 29, 2017. (Photo by Carlos Eduardo Ramirez/Reuters)

Inês Carvalho (C), accompanied by her sister and cousin, is helped by her aunt to dress up at Alfama neighborhood in Lisbon on June 12, 2014. Carvalho, 18, is one of the revelers from the Alfama march and every Saint Anthony's day, Lisbon's protector, she parades with several other typical neighborhoods of the city. (Photo by Patricia De Melo Moreira/AFP Photo)

Men slide in the mud during the Boryeong Mud Festival at Daecheon Beach in Boryeong, South Korea, Saturday, July 22, 2017. The 20th annual mud festival features mud wrestling and mud sliding. (Photo by Ahn Young-joon/AP Photo)