Children play during a Christmas party organised by the Peacekeeping Unit Program (UPP) at the Cantagalo slum in Rio de Janeiro December 17, 2011. The introduction of the peacekeeping program in the region is part of an effort to crack down on crime and ensure security as the city prepares to host the 2014 World Cup and the 2016 Olympic Games. REUTERS/Sergio Moraes (BRAZIL - Tags: SOCIETY POVERTY)