Pupils of the Dao ethnic tribe return home from school along a hillside path at Suoi Thau village in Hoang Su Phi district of Vietnam's northern province of Ha Giang, located at the border with China, September 18, 2015. (Photo by Reuters/Kham)

Vendors selling marigold garlands, which are used to decorate temples and homes during the Hindu festival of Durga Puja, drink tea as they wait for customers at a wholesale flower market in Kolkata, India October 6, 2016. (Photo by Rupak De Chowdhuri/Reuters)

A man dressed as the “Star Wars” character Darth Vader sits on a bench in central Lviv, Ukraine, November 24, 2016. (Photo by Gleb Garanich/Reuters)

“DC3 Wreck”. A capture of a US military DC3 plane wreck at the southern black beach in Iceland. Photo location: Iceland. (Photo and caption by Naian Feng/National Geographic Photo Contest)

China's Shang Chunsong prepares to compete in the uneven bars event of the women's individual all-around final artistic gymnastics competition at the Namdong Gymnasium Club during the 17th Asian Games in Incheon, in this September 23, 2014 file photo. (Photo by Kim Hong-Ji/Reuters)

Robert Burck, a street performer known as “The Naked Cowboy” dips a woman as he poses for a photo in Times Square in New York, U.S., August 4, 2016. (Photo by Carlo Allegri/Reuters)

A German special anti-tank gun is ready to fire during the army maneuvers in Silesia, Poland, on September 22, 1928. (Photo by AP Photo)

His own space suit, with oxygen tank, doesn't make Barney the monkey any happier as he and actor Adam West view the situation in their space capsule in Hollywood on January 24, 1964. Barney, a South American woolly monkey, is blasted into space with West, as an astronaut, in a new movie, “Robinson Crusoe on Mars”. (Photo by AP Photo)