Students from Langata primary school run past riot police as they protest against a perimeter wall illegally erected by a private developer around their school playground in Kenya's capital Nairobi January 19, 2015. Riot police used teargas to disperse students at a school in Nairobi as the children protested against the potential loss of their playground. The playground was fenced off in December, during the school holidays, by a prominent developer who also claims ownership of the land. The title to the contested site is said to be in the name of Airport View Housing Limited, according to local media, with plans to use the space to build a parking lot for a hotel. (Photo by Thomas Mukoya/Reuters)

Young people fight for fun with their pillows, during the International Pillow Fight Day at the Place des Grottes, in Geneva, Switzerland, Saturday, April 4, 2015. The annual International Pillow Fight Day takes place in hundreds of cities around the world. (Photo by Salvatore Di Nolfi/AP Photo/Keystone)

Members of the Bolivian combined forces of army and police rest at their headquarters at the end of their ceremony for the task of fighting against drugs and the eradication of coca leaves in Chimore, east of La Paz, December 10, 2014. The government of Bolivia's President Evo Morales eradicated some 11,000 hectares of illegal coca plants and confiscated nearly 192 tons of drugs in 2014, according to the local media. (Photo by David Mercado/Reuters)

Claudia Gadelha (L) of Brazil fights with Jessica Aguilar of Mexico during their Ultimate Fighting Championship (UFC) match, a professional mixed martial arts (MMA) competition in Rio de Janeiro, Brazil August 1, 2015. (Photo by Ricardo Moraes/Reuters)

Members of the “Familia Gladiatoria Carnuntina” fight in the historic amphitheatre during the Roman Festival at the archeological site of Carnuntum in Petronell, Austria, June 11, 2016. (Photo by Leonhard Foeger/Reuters)

Long Exposure pictures showing Mount Sinabung spewing out hot lava on August 2, 2017 in Karo, Indonesia. Sinabung located in North Sumatra Province roared back to life in 2010 for the first time in 400 years. After another period of inactivity it erupted once more in 2013, and has remained highly active since. (Photo by Albert Damanik/Barcroft Images)

A pilot steers his helicopter at night over Rio de Janeiro, Brazil, less than two weeks before the start of the Rio 2016 Olympic Games, July 23, 2016. Picture taken July 23, 2016. (Photo by Pawel Kopczynski/Reuters)

Tiny pieces of space rocks, called meteorites, are seen burning in the atmosphere over the night sky near Salgótarján, some 109km northeast of Budapest, Hungary, 21 April 2018 (issued 22 April 2018). (Photo by Peter Komka/EPA/EFE)