Demonstrators perform a dance in front of riot policemen during a march called by students to request changes in the education system in Santiago, Chile September 5, 2017. (Photo by Ivan Alvarado/Reuters)

In this October 21, 2015, file photo, a young man rides a hoverboard along a Manhattan street toward the Empire State Building in New York. More than 500,000 hoverboards are being recalled after reports that they can burst into flames. The Consumer Product Safety Commission said Wednesday, July 6, 2016, it has received 99 reports of battery packs in the two-wheel motorized scooters catching fire or exploding that causing burns or property damage. The recalled hoverboards were made by eight companies. (Photo by Kathy Willens/AP Photo)

Two boys in the Gorbals area of Glasgow, UK on January 31, 1948. The Gorbals tenements were built quickly and cheaply in the 1840s, providing housing for Glasgow's burgeoning population of industrial workers. Conditions were appalling; overcrowding was standard and sewage and water facilities inadequate. The tenements housed about 40,000 people with up to eight family members sharing a single room, 30 residents sharing a toilet and 40 sharing a tap. By the time this photograph was taken 850 tenements had been demolished since 1920. Redevelopment of the area began in the late 1950s and the tenements were replaced with a modern tower block complex in the sixties. (Photo by Bert Hardy/Getty Images)

A man runs away during a police round up of suspected drug addicts in Kabul, Afghanistan December 27, 2015. Afghan officials have opened a new drug treatment centre in an abandoned NATO military base in Kabul, in the latest attempt to stamp out the country's massive problem of drug abuse. Camp Phoenix, a former training camp on the edges of Kabul set up by the U.S. army in 2003, will take in around 1,000 homeless drug addicts who will receive food, medical attention and treatment, said Public Health Minister Ferozuddin Feroz. (Photo by Ahmad Masood/Reuters)

People collect water from shallow wells dug along the Shabelle River bed, which is dry due to drought in Somalia's Shabelle region, March 19, 2016. The cabinet ministers of the federal republic of Somalia have held on Thursday their weekly meeting in Mogadishu and discussed on the drought situation in parts of the country and its humanitarian consequences. Chaired by the acting PM and justice minister Abdullah Ahmed Jama (Ilka-Jir), the cabinet noted with deep concern the the prevailing situation in Somalia, with one of the worst ever drought in two decades. (Photo by Feisal Omar/Reuters)

A girl rides a donkey as another walks by at the Shawqaba camp for internally displaced people who were forced to leave their villages by the war in Yemen's northwestern province of Hajjah March 12, 2016. In northwest Yemen, one of the poorest countries in the Middle East, about 400 families uprooted by the war have been stuck in the Shawqaba camp in Hajjah province for the past year. Residents live in poorly built huts that protect them neither from summer heat nor winter cold in a camp that lacks the most basic services. (Photo by Abduljabbar Zeyad/Reuters)

The Breitling DC-3, HB-IRJ, plane fly escorted by Italian Air Force's aerobatic demonstration team, the Frecce Tricolori, during the last stage of its world tour two days ahead of the International Sion Air Show, in Sion, Switzerland, 13 September 2017. From March to September 2017, the Breitling DC-3 from 1940 has done a grand world tour in several stages, over 28 countries and flies 50000km, an amazing accomplishment for this legendary plane that will be celebrating its 77th birthday. (Photo by Christian Merz/EPA/EFE)

In this May 24, 2016 photo, a young boy descends the Qullqip'unqu mountain looking out at the tens of thousands of pilgrims gathered to celebrate the three-day festival Qoyllur Rit’i, translated from the Quechua language as Snow Star, in the Andean Sinakara Valley, in Peru's Cusco region. The celebration that mixes Catholic and indigenous beliefs honors Jesus as well as the area’s glacier, which is considered sacred among some indigenous people. While the native celebration is far older, the Christian part of the ritual stretches back to the 1700s, when Jesus is said to have appeared to a young shepherd in the form of another boy. (Photo by Rodrigo Abd/AP Photo)