A rescue helicopter is shown at the Mount Everest south base camp in Nepal a day after a huge earthquake-caused avalanche killed at least 17 people, in this photo courtesy of 6summitschallenge.com taken on April 26, 2015 and released on April 27, 2015. Rescue teams, helped by clear weather, used helicopters to airlift scores of people stranded at higher altitudes, two at a time. (Photo by Reuters/6summitschallenge.com)

Cuban girls dressed as nurses and a lizard wait for their turn to dance during a visit by the Gay Men's Chorus of Washington in Havana July 13, 2015. The choir made its first appearance on July 12, 2015 in Cuba as part of a tour that will include a dozen concerts in the context of the restoration of relations between the island and the United States. (Photo by Enrique de la Osa/Reuters)

A dirty thunderstorm occurs over Mount Sakurajima as the volcano erupts violently at 12:03 am on July 26, 2016 in Tarumizu, Kagoshima, Japan. The eruption occurred at the mountain's Showa crater. This is the first time that the active volcano in southern Kyushu has spewed out a smokestack that high since an eruption on August 18, 2013, according to the Kagoshima Meteorological Office. (Photo by The Asahi Shimbun via Getty Images)

A military instructor helps a boy to shoot a rifle with blanks at a weapon exhibition during a military show in St.Petersburg, Russia, Sunday, January 17, 2016. (Photo by Dmitry Lovetsky/AP Photo)

A damaged traffic signal is pictured along a street at a residential area flooded by the Kinugawa river, caused by typhoon Etau in Joso, Ibaraki prefecture, Japan, September 11, 2015. Unprecedented rain in Japan unleashed heavy floods on Friday that tore houses from their foundations, uprooted trees and forced more than 100,000 people from their homes. (Photo by Issei Kato/Reuters)

A racegoer is given some water as he lays on the ground following 2017 Stakes Day at Flemington Racecourse on November 11, 2017 in Melbourne, Australia. (Photo by Scott Barbour/Getty Images)

A female member of Romania's military adjusts her hat before taking part in the national day military parade in Bucharest, Romania, Friday, December 1, 2017. Thousands of Romanian troops staged a military parade to celebrate Romania's national day, but key politicians didn't attend, signaling tensions between the president and the ruling left-wing coalition over plans to revamp the justice system. (Photo by Vadim Ghirda/AP Photo)

A spectator cools herself at a water spraying fan at the Australian Open tennis championships in Melbourne, Australia, Tuesday, January 17, 2017. (Photo by Kin Cheung/AP Photo)