An Afghan National Army (ANA) soldier assigned to the Mobile Strike Force Kandak fires a RPG-7 rocket-propelled grenade launcher during a live-fire exercise supervised by the Marines with the Mobile Strike Force Advisor Team on Camp Shorabak, Helmand province, Afghanistan, May 20, 2013. The Marines with the Mobile Strike Force Advisor Team instructed and mentored their ANA counterparts on how to properly utilize their weapons systems. (Photo by SSgt Ezekiel R. Kitandwe/RCT 7)

Five year old George holds an orange to feed the Owl butterflies at the Natural History Museum in London, Thursday, March 30, 2017. Hundreds of tropical butterflies were released to launch the Natural History Museum's Sensational Butterflies exhibition, starting for the public on March 31, 2017. (Photo by Frank Augstein/AP Photo)

A person jumps on a trampoline before Nathan's Famous Fourth of July International Hot Dog-Eating Contest at Coney Island in Brooklyn, New York City, U.S., July 4, 2017. (Photo by Andrew Kelly/Reuters)

Skiers and snow boarders descend from a slope as they attempt to break the record for mass skiing in swimming suits at Rosa Khutor resort near Sochi, Russia, April 9, 2016. (Photo by Kazbek Basayev/Reuters)

The Breitling DC-3, HB-IRJ, plane fly escorted by Italian Air Force's aerobatic demonstration team, the Frecce Tricolori, during the last stage of its world tour two days ahead of the International Sion Air Show, in Sion, Switzerland, 13 September 2017. From March to September 2017, the Breitling DC-3 from 1940 has done a grand world tour in several stages, over 28 countries and flies 50000km, an amazing accomplishment for this legendary plane that will be celebrating its 77th birthday. (Photo by Christian Merz/EPA/EFE)

A street actor dressed as a devil frightens children in downtown Prague in Prague, Czech Republic, Monday, December 5, 2016. On the eve of St. Nicholas, Czechs traditionally celebrate by dressing up as Devils, Angels and St. Nicholas, and visiting children in their homes handing out small presents, coal, potatoes or other gifts. (Photo by Petr David Josek/AP Photo)

Crown line handler Bobby Marie controls “Chain Gang” as the balloon is inflated during the 43nd Annual Helen to the Atlantic Balloon Race and Festival, in Helen, Georgia, USA, 04 June 2016. The race is the oldest balloon event in the southern USA and United States' only long-distance hot air balloon race, according to the organizers. (Photo by Erik S. Lesser/EPA)

A roadside currency exchange vendor sorts Indian currency notes at his stall in Agartala, India, December 6, 2016. (Photo by Jayanta Dey/Reuters)