Schoolchildren perfom during celebrations to mark 35 years of Zimbabwe's Independence at the National sports stadium in Harare, Saturday, April 18, 2015. President Robert Mugabe, 91, the central figure in Zimbabwean politics 35 years after Independence from Britain, has led the country since 1980. (Photo by Tsvangirayi Mukwazhi/AP Photo)

Andrew Hepher, Vice President of Lubricants Technology, Shell unveils the Shell Concept Car in Beijing, China, Friday, April 22, 2016. Built as proof of energy efficiency that can be achieved with the latest technologies, Shell unveiled the concept car ahead of the bi-annual Beijing Auto Show where the world's top car manufacturers will showcase their own upcoming products. (Photo by Ng Han Guan/AP Photo)

In this March 18, 2015 photo, Andrea, better known as Loira, which is the Portuguese word for “blonde”, poses for a portrait in an open-air crack cocaine market, known as a “cracolandia” or crackland where users can buy crack, and smoke it in plain sight, day or night, in Rio de Janeiro, Brazil. Andrea says she is married and has a home, but she keeps returning to crackland to feed her addiction. (Photo by Felipe Dana/AP Photo)

The front wheels of a tractor, pulling a trailer overloaded with sugarcane, are seen lifted off the ground as it passes through the streets of Karor Lan Esan, Pakistan December 6, 2015. (Photo by Caren Firouz/Reuters)

Characters dressed as Elmo and Cookie Monster who pose for tips take a photo by request from a tourist (2nd R, black pants) in Times Square in the Manhattan borough of New York City, January 29, 2016. (Photo by Rickey Rogers/Reuters)

A man is silhouetted as he stands on a walkway in the sky lobby at the Chancellery, the seat of German Chancellor Angela Merkel (not pictured) in Berlin, May 7, 2014. (Photo by Thomas Peter/Reuters)

Ramoncito Campo kisses his wife Hernelie Ruazol Campo on a flooded street during a southwest monsoon that battered Manila August 8, 2012. The newly-wed couple pushed through with their scheduled wedding despite severe flooding that inundated wide areas of the capital and nearby nine provinces. (Photo by Reuters/Courtesy of Ramoncito Campo)

Women wearing sunglasses pose for a group photo at a park in Beijing in 1980. (Photo by Reuters/China Daily)