An injured fan is helped by a riot policeman during clashes between Red Star Belgrade and Partizan Belgrade fans in the stadium before the teams' Serbian Superliga soccer match in Belgrade, April 25, 2015. Serbian league leaders Partizan Belgrade held champions and bitter city foes Red Star to a 0-0 draw in a derby match marred by bad crowd trouble before kickoff on Saturday. The start was delayed for 45 minutes after home Red Star supporters pelted riot police with seats and flares, forcing officers to retreat from the north tier that houses the club's diehard fans. (Photo by Marko Djurica/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)

Club-goers dance at “Morning Gloryville” at the Ministry of Sound in south London August 11, 2015. Morning dance parties with names like “Morning Gloryville” and "Daybreaker" are gathering steam in cities across the world, giving rise to a movement known as “conscious clubbing”. Its founders aim to create the energy and community of electronic dance parties with fruit smoothies and coffee instead of the drugs and alcohol more common after nightfall. (Photo by Toby Melville/Reuters)

Women dance in costume during the West Indian Day Parade in Brooklyn, New York September 7, 2015. The parade, which takes place annually, celebrates Caribbean culture and history. (Photo by Andrew Kelly/Reuters)