Riot police fire tear gas during a protest by supporters of Dilma Rousseff in Sao Paulo, Brazil August 31, 2016. (Photo by Paulo Whitaker/Reuters)

A pilot steers his helicopter at night over Rio de Janeiro, Brazil, less than two weeks before the start of the Rio 2016 Olympic Games, July 23, 2016. Picture taken July 23, 2016. (Photo by Pawel Kopczynski/Reuters)

A tomtit bird flies past a squirrel running on a fence after a snowfall in a park in Almaty, Kazakhstan, January 12, 2016. (Photo by Shamil Zhumatov/Reuters)

A partial solar eclipse is seen as a labourer works at a construction site in Phnom Penh, Cambodia, March 9, 2016. (Photo by Samrang Pring/Reuters)

A bakery worker rides a bicycle as he carries fresh bread on his head in Cairo, Egypt, February 9, 2016. (Photo by Asmaa Waguih/Reuters)

A dog walker on Longsands beach before sunrise in Tynemouth, UK on April 1, 2016. (Photo by Owen Humphreys/PA Wire)

Cocoa pods are seen on the ground at a farm in Ile-Oluji village in Ondo state, southwest Nigeria March 29, 2016. (Photo by Akintunde Akinleye/Reuters)

A subway worker walks away after a train departed the station in central Pyongyang, North Korea May 7, 2016. (Photo by Damir Sagolj/Reuters)