Residents observe a police officer take up position during an operation at the Mare slums complex in Rio de Janeiro March 25, 2014. The federal troops have taken control of security operations in Mare slums complex to help quell a surge in violent crime following attacks by drug traffickers on police posts in three slums on the north side of the city, government officials said. (Photo by Ricardo Moraes/Reuters)

A participant takes part in the Bristol Park and Slide project, an interactive temporary installation by artist Luke Jerram set up in Park Street in the centre of Bristol, southwest England on May 4, 2014. Over 95,000 people applied for just 360 tickets to slide on inflatable lilos down a lubricated water slide in a town centre street. (Photo by Leon Neal/AFP Photo)

Fisherwomen laying barrels with salt in preparation for herring curing, 1937. (Photo by Topical Press Agency)

A baby Chimpanzee plays in its enclosure at Taronga Zoo July 14, 2006 in Sydney, Australia. (Photo by Ian Waldie/Getty Images)

A model walks down the runway at the 13th China International Young Fashion Designers Contest during China Fashion Week on March 25, 2005 in Beijing, China. (Photo by China Photos/Getty Images)

Afghan men work in a small sweets factory in Kabul, Afghanistan January 5, 2017. (Photo by Mohammad Ismail/Reuters)

Rob, a British man in his late 20's in Magaluf, Majorca on his stag party, kisses a participant in a wet t-shirt competition hosted at Mambo's Terrace on June 28, 2013. (Photo by Peter Dench/Getty Images Reportage)

A hillside erupts in flame as a raging wildfire fire burns in Placerita Canyon in Santa Clarita, Calif., Monday, July 25, 2016. A raging wildfire that forced thousands from their homes on the edge of Los Angeles continued to burn out of control Monday as frustrated fire officials said residents reluctant to heed evacuation orders made conditions more dangerous and destructive for their neighbors. (Photo by Nick Ut/AP Photo)