First graders of a cadet's lyceum attend a ceremony to mark the start of the new school year in Kiev, Ukraine, September 1, 2015. September 1 marks the start of a new academic year for students in Ukraine.(Photo by Valentyn Ogirenko/Reuters)

First graders attend a festive ceremony to mark the start of another school year in Slaviansk, September 1, 2014. September 1 marks the start of a new academic year for students in Ukraine. (Photo by Gleb Garanich/Reuters)

Shoppers walk down stairs featuring a five-metre-high reproduction of Vincent van Gogh's signature painting “Sunflowers”, at the entrance to Ocean Terminal in Hong Kong July 15, 2013. A premium three-dimensional reproduction of works of Van Gogh, the RELIEVO collection, approved by the curators of the Van Gogh Museum in Amsterdam, is on display at a gallery inside Harbour City shopping mall attached to the terminal. (Photo by Bobby Yip/Reuters)

A boat, center, is surrounded by Japan Cost Guard's patrol boats after some activists descended from the boat on Uotsuri Island, one of the islands of Senkaku in Japanese and Diaoyu in Chinese, in East China Sea Wednesday, Aug. 15, 2012. Regional tensions flared on the emotional anniversary of Japan's World War II surrender as activists from China and South Korea used Wednesday's occasion to press rival territorial claims, prompting 14 arrests by Japanese authorities. The 14 people had traveled by boat from Hong Kong to the disputed islands controlled by Japan but also claimed by China and Taiwan. (Photo by Yomiuri Shimbun/Masataka Morita/AP Photo)

Autos sit on top of each other in a washed out section of Dog Track Road in the Millview community as Gulf Coast residents continue cleaning up from damage caused by torrential rains in Pensacola, Fla., Thursday, May 1, 2014. The National Weather Service, estimated 15-20 inches of rain has fallen in the Pensacola area in the past 2 days. (Photo by G. M. Andrews/AP Photo)

Strokkur geyser against cloudy sky at sunset. Strokkur is a fountain geyser located in a geothermal area beside the Hvítá River in Iceland in the southwest part of the country, east of Reykjavík. It is one of Iceland's most famous geysers, erupting once every 6–10 minutes. Its usual height is 15–20 m, although it can sometimes erupt up to 40 m high. (Photo by Teatsche Dijkhuis/Getty Images/EyeEm)

In this October 15, 2014 file photo, Katsu Nakamura, sky division manager for Yamaha USA, moves the RMax unmanned helicopter into position before a demonstration of its aerial application capabilities at the University of California, Davis' Oakville Station test vineyard in Oakville, Calif. Researchers at UC Davis have been studying the effectiveness of the drone's ability for spraying pest control and nutritional materials on the test vineyard in California's Napa Valley. (Photo by Rich Pedroncelli/AP Photo)

Hindu holy man, or sadhu, applies paint to his forehead at his ashram on the premises of Pashupatinath Temple in Kathmandu February 15, 2015. Hindu holy men from Nepal and India come to this temple to take part in the Maha Shivaratri festival. Celebrated by Hindu devotees all over the world, Shivaratri is dedicated to Lord Shiva, and holy men mark the occasion by praying, smoking marijuana or smearing their bodies with ashes. (Photo by Navesh Chitrakar/Reuters)