A competitor participates in the Tough Mudder challenge near Henley-on-Thames in southern England May 2, 2015. (Photo by Eddie Keogh/Reuters)

A helicopter drops water over a wildfire as a firefighter works to contain it in Benahavis, southern Spain, May 19, 2015. (Photo by Jon Nazca/Reuters)

A participant smiles at the annual Christopher Street Day parade on Kurfuerstendamm in Berlin, Germany, June 27, 2015. (Photo by Fabrizio Bensch/Reuters)

A girl uses her mobile phone during the evening at the National Park in Khartoum, Sudan, April 24, 2015. (Photo by Mohamed Nureldin Abdallah/Reuters)

A reveler gets ready to perform at a carnival parade in Havana, Cuba August 7, 2015. (Photo by Alexandre Meneghini/Reuters)

An Afghan man works at a traditional yarn factory in Heart province, Afghanistan July 28, 2015. (Photo by Mohammad Shoib/Reuters)

A dog jumps over an obstacle during the International Agility Riga Cup competition in Riga, Latvia, August 15, 2015. (Photo by Ints Kalnins/Reuters)

Revellers watch as police officers dance in the street at the Notting Hill Carnival in west London, August 30, 2015. (Photo by Toby Melville/Reuters)