A child rescued from Boko Haram in Sambisa forest is seen at the Internally Displaced People's camp in Yola, Nigeria May 3, 2015. Hundreds of traumatised Nigerian women and children rescued from Boko Haram Islamists have been released into the care of authorities at a refugee camp in the eastern town of Yola, an army spokesman said. (Photo by Afolabi Sotunde/Reuters)

Revelers dance and shout as they listen to music, in front of the main stage, during the 21st Woodstock Festival in Kostrzyn-upon-Odra, Poland July 31, 2015. An estimated 200,000 people attended the ongoing festival, a brainchild of Polish journalist and social campaigner Jerzy Owsiak, on Friday. Owsiak initiated the event to say thank you to those who donated money to his GOCC charity organisation that delivers medical care for children. (Photo by Kacper Pempel/Reuters)

Four-year-old Chinese boy Huang Yang plays with five-year-old beluga whale Xiao Xin at the Qingdao Ocean World on November 3, 2007 in Qingdao of Shandong Province, China. Huang Yang began swimming as a baby and fell in love with the whale after watching its performance. On the International Children's Day, June 1 this year, the Qingdao Ocean World has made the boy's dream come true when they allowed Huang Yang to swim with the beluga whale. (Photo by China Photos/Getty Images)

Santa Claus rides in his sleigh as he prepares for Christmas in the Arctic Circle near Rovaniemi, Finland December 15, 2016. At Santa Claus' Lapland home in Finland, his helpers sort out piles of letters from around the world, each detailing children's requests for this Christmas. (Photo by Pawel Kopczynski/Reuters)

In this handout image provided by the Police of Swiss canton Valais the wreckage of a bus is seen after it crashed inside a motorway tunnel on March 13, 2012 in Sierre, Switzerland. 28 people, including 22 children, returning from a skiing holiday died in this bus accident. (Photo by Police Cantonale Valaisanne via Getty Images)