Ingots of 99.99 percent pure silver are cast at the Krastsvetmet Krasnoyarsk non-ferrous metals plant in the Siberian city of Krasnoyarsk, Russia, June 5, 2015. Krastsvetmet is one of the world's largest players in the precious metals industry. REUTERS/Ilya Naymushin

In this photo taken on Sunday, July 5, 2015, police officers walk along a giant poster to give an improved appearance, in downtown Ufa, Russia. Ufa will host SOC (Shanghai Cooperation Organization) and BRICS (Brazil, Russia, India, China and South Africa) summits July 7 to July 9, 2015. (Photo by Vadim Braydov/AP Photo)

A worker settles mud in a mold to make bricks at a brick factory in Tixtla, on the outskirts of Chilpancingo, in the Guerrero state, January 26, 2015. The worker earns a salary of 15 Mexican pesos, or one dollar, for every 100 bricks made on a working day of at least 5 hours. (Photo by Jorge Dan Lopez/Reuters)

Miss Venezuela Edymar Martinez poses during the swimsuit contest during the Miss International beauty pageant in Tokyo on November 5, 2015. Martinez won the Miss International title. Representatives of 70 countries and regions from all over the world took part in the annual beauty contest. (Photo by Toru Yamanaka/AFP Photo)

Shepherd Ben Blackmore stands with his flock of Exmoor Horn sheep in Savile Row, London, Britain October 5, 2015. The Campaign for Wool marked the beginning of Britain's national Wool Week on Monday, on one of London's most renowned streets. (Photo by Peter Nicholls/Reuters)

A Sumatran Tiger looks at visiting children from it's enclosure during the ZSL London Zoo's annual stocktake of animals on January 5, 2015 in London, England. The zoo's annual stocktake requires keepers to check on the numbers of every one of the 800 different animal species, including every invertebrate, bird, fish, mammal, reptile, and amphibian. (Photo by Dan Kitwood/Getty Images)

In this Saturday, September 5, 2015, photo, three women in costumes look at sea life swimming above them during a private party held at the Georgia Aquarium as part of Dragon Con in Atlanta. The convention draws fans from around the country to take part in sci-fi and fantasy costume contests, a massive parade through downtown Atlanta and educational seminars about science and costume making. (Photo by Ron Harris/AP Photo)

Aerobatic aircrafts fly during a performance at the Airshow Zhengzhou 2017 in Zhengzhou, capital of central China's Henan Province on April 27, 2017. The 5-day air show kicked off in Zhengzhou on Thursday, aiming to build a general aviation gathering center for business and communications. (Photo by Li An/Xinhua via ZUMA Wire)