A pile of destroyed cars of teachers sits outside Briarwood elementary school in Oklahoma City, Oklahoma May 22, 2013. Rescue workers with sniffer dogs picked through the ruins on Wednesday to ensure no survivors remained buried after a deadly tornado left thousands homeless and trying to salvage what was left of their belongings. Curvature of horizon in the photo is due to an ultra-wide angle lens. (Photo by Rick Wilking/Reuters)

Rescue workers try to pull out a piece of an exploded Grad missile outside an apartment building in Vostochniy district of Mariupol, Eastern Ukraine, Sunday, January 25, 2015. Indiscriminate rocket fire slammed into a market, schools, homes and shops Saturday in Ukraine's southeastern city of Mariupol, killing at least 30 people, authorities said. The Ukrainian president called the blitz a terrorist attack and NATO and the U.S. demanded that Russia stop supporting the rebels. (Photo by Evgeniy Maloletka/AP Photo)

Riot Police form a cordon as a Police car burns on the opening day of the European Central Bank (ECB) in Frankfurt am Main, western Germany, on March 18, 2015. Supporters of the so-called Blockupy alliance consisting of social movements, activists, workers, trade unions and parties are expected to stage large protests against austerity and the authority of the European Central Bank when the bank's new headquarters officially will be on March 18, 2015. (Photo by Odd Andersen/AFP Photo)

In this photo taken on Saturday, April, 4, 2015, a bear chews on a corncob at a shelter that attracts hundreds of visitors and volunteers from around the world every year, in Kutarevo, Croatia. Over a decade ago, Ivan Crnkovic-Pavenka, a retired Croatian social worker decided to help bears become “ambassadors of the wilderness” among people and set up a unique shelter for brown bears in the idyllic mountain village of Kutarevo in central Croatia, where eight bears currently live in two huge enclosures. (Photo by Amel Emric/AP Photo)

A woman in traditional clothes wears a pin showing North Korea's founder Kim Il-sung (L) and former leader Kim Jong-il, on her dress as she welcomes foreign reporters to a temple during a government organised tour just outside Pyongyang October 8, 2015. North Korea is getting ready to celebrate the 70th anniversary of the founding of its ruling Workers' Party of Korea on October 10. (Photo by Damir Sagolj/Reuters)

North Korean leader Kim Jong Un (3rd R) and wife Ri Sol Ju (4th L) enjoy an art performance given by the Chongbong Band to mark the 70th anniversary of the founding of the Workers' Party of Korea (WPK) in this undated photo released by North Korea's Korean Central News Agency (KCNA) in Pyongyang on October 19, 2015. (Photo by Reuters/KCNA)

A parishioner of the St. Joseph the Worker Parish in Nairobi's Kangemi slum carries the vestments to be worn by Pope Francis during his visit to Kenya on November 24, 2015 in Kenya. Pope Francis makes his first visit to Kenya on a five day African tour that is scheduled to include Uganda and the Central African Republic. Africa is recognised as being crucial to the future of the Catholic Church with the continent's Catholic numbers growing faster than anywhere else in the world. (Photo by Nichole Sobecki/Getty Images)

Medics help a rescued miner after an explosion and fire at a coal mine killed at least 17 miners and left up to 300 workers trapped underground, in Soma, in western Turkey, Tuesday, May 13, 2014, a Turkish official said. Twenty people were rescued from the mine but one later died in the hospital, Soma administrator Mehmet Bahattin Atci told reporters. The town is 250 kilometers (155 miles) south of Istanbul. The death toll was expected to rise. (Photo by AP Photo/Depo Photos)