A young man, who says he is part of a local criminal gang, poses for a picture holding a gun in the neighbourhood of Korogcho in Nairobi, Kenya, March 19, 2015. Around 2 million people live in the shantytowns packed in around Kenya's capital. Crime is high amid chronic unemployment levels, while basic services and sanitation are scarce. Residents try to make the best of things, eking out a living and picking up work where they can. (Photo by Siegfried Modola/Reuters)

Vladimir Putin looks at a model of the Tupolev TU-160 bomber, or Blackjack, that was presented to him on his arrival in Olenegorsk, Russia, August 16, 2005. Putin flew in the Tupolev TU-160 bomber and took part in the launch of cruise missiles in the Arctic north. (Photo by Reuters/ITAR-TASS/Presidential Press Service)

Competitors take part in the Christmas Really Wild Mud Run on a 4.6 miles course across undulating farm land at Celtic Camping, St David's, Pembrokeshire, Wales, December 12, 2015. (Photo by Rebecca Naden/Reuters)

Yakelin Hernandez, 18, poses for a photograph near The Malecon where The Carnival was held, on August 14, 2015. Colorful costumes, dancing, parades and street parties on the Malecon in Havana, Cuba are all part of Havana Carnival 2015 which was held in August. (Photo by Sarah L. Voisin/The Washington Post)

Inmates stand next to food during a Christmas event at Sarita Colonia male prison in Callao, Peru, December 18, 2015. For the event, inmates prepared Christmas meals for a culinary competition and took part in dances and songs. (Photo by Mariana Bazo/Reuters)

People in Kathmandu joke that the face mask has now become part of the national dress – an indispensable accessory in an effort to protect themselves from the dust. Nepal has the worst air quality in the world, according to the Environmental Performance Index. (Photo by Pete Pattisson/The Guardian)

A woman wearing a wedding dress takes part in the so-called “brides' match” at the FIFA Fan Fest in Kazan, a host city for the 2018 FIFA World Cup, Russia June 30, 2018. (Photo by Alexey Nasyrov/Reuters)

Two brave contestants take part in the World Gravy Wrestling Championships at the Rose 'n Bowl in Stacksteads, Lancashire, England on August 27 2018. Contestants must wrestle in the gravy for 2 minutes, points are scored for fancy dress, comedy effect, entertainment and wrestling ability. The event is held to raise funds for the East Lancashire Hospice and competitors nominated charities. (Photo by The Mercury Press)