Performers of circus company Circa perform during a photocall for the Edinburgh Festival Fringe on Calton Hill on August 1, 2017 in Edinburgh, United Kingdom. (Photo by Murdo MacLeod/The Guardian)

A member of Iraqi rapid response forces fires a rocket launcher during a battle with Islamic State militants in the district of Yarimja in southern Mosul, Iraq, January 18, 2017. (Photo by Alaa Al-Marjani/Reuters)

A traffic police woman whistles at a pedestrian, Monday, July 27, 2015, in Pyongyang, North Korea where its citizens are having a one-day national holiday to celebrate the country's 62nd anniversary of the armistice that ended the Korean War. (Photo by Wong Maye-E/AP Photo)

Mount Sinabung is seen during an eruption from Surbakti village in Karo, North Sumatra, Indonesia, April 20, 2015. The local government is preparing the relocation of residents from three of the villages that were destroyed. (Photo by Tibta Pangin/Getty Images/Anadolu Agency)

Framed by the setting sun, an American Bison grazes at the Tallgrass Prairie National Preserve on Tuesday, April 28, 2015, near Strong City, Kan. The buffalo herd at Tallgrass is one of the few herds of wild bison left in the United States. (Photo by Travis Heying/The Wichita Eagle via AP Photo)

A woman wearing a mask reacts at her garden which locates next to chimneys of coal-fired power plant in Shijiazhuang, Hebei province, China, January 28, 2015. Beijing introduced tougher regulations this year to combat pollution, keen to overhaul China's unwanted image of smog-choked cities, fouled waterways and heavy-metal tainted soil. (Photo by Kim Kyung-Hoon/Reuters)

Samburu tribesmen stand during the Maralal Camel Derby, Kenya, August 15, 2015. Maralal, a small, arid town about an eight-hour drive north of the Kenyan capital Nairobi, holds an annual camel festival, bringing together members of the Samburu, Turkana and Pokot semi-nomadic cattle-herding tribes. (Photo by Goran Tomasevic/Reuters)

A man runs away during a police round up of suspected drug addicts in Kabul, Afghanistan December 27, 2015. Afghan officials have opened a new drug treatment centre in an abandoned NATO military base in Kabul, in the latest attempt to stamp out the country's massive problem of drug abuse. Camp Phoenix, a former training camp on the edges of Kabul set up by the U.S. army in 2003, will take in around 1,000 homeless drug addicts who will receive food, medical attention and treatment, said Public Health Minister Ferozuddin Feroz. (Photo by Ahmad Masood/Reuters)