South Korean police officers show their martial arts' skills during the official launch ceremony of the 2012 Seoul Nuclear Security Summit on February 15, 2012 in Seoul, South Korea. The Korean National Police Agency launched a security squad, exclusively established for the successful hosting of the 2012 Seoul Nuclear Security Summit. The 2012 Seoul Nuclear Security Summit will be held in Seoul from March 26-27, 2012. (Photo by Chung Sung-Jun/Getty Images)

People take part in a Halloween street party at Lan Kwai Fong on October 31, 2016 in Hong Kong. Halloween, a contraction of All Hallows' Evening, falls on the day before All Saints' Day on November 1, a holiday when Christians remember their deceased loved ones. (Photo by Lam Yik Fei/Getty Images)

Combine harvesters work on a wheat field of the Solgonskoye farming company near the village of Talniki, southwest from Siberian city of Krasnoyarsk, Russia, August 27, 2015. Russia, one of the world's top wheat exporters, will harvest its third-largest grain crop in post-Soviet history this year, leading Russian consultancy SovEcon said on August 27 after upgrading its forecast. (Photo by Ilya Naymushin/Reuters)

Giant panda Mei Xiang discovers a birthday cake meant for her cub Bei Bei (NP) who turns one at the Smithsonian National Zoo in Washington, DC on August 20, 2016. (Photo by Linda Davidson/The Washington Post)

Pedestrians are falling after a gust of wind in Munich southern Germany, Tuesday, March 31, 2015. One of the strongest storm fronts in years hit Germany on Tuesday, as Storm “Niklas” uncovered roofs, toppled scaffolding and caused severe disruption to rail services. (Photo by Sven Hoppe/AP Photo/DPA)

Central Bangkok and the Chao Phraya River are seen from an abandoned skyscraper in Bangkok April 19, 2015. The abandoned building, known as Satorn Unique, dubbed the “ghost tower” was destined to become one of Bangkok's most luxurious residential addresses but construction was never completed as the Thai economy was hit during the 1997 Asian Financial Crisis. Now, many travellers visit and explore 49-storey skyscraper. (Photo by Athit Perawongmetha/Reuters)

These black-and-white photos are taken from the new book “Armoured Warfare in the First World War 1916 – 1918” by Anthony Tucker-Jones and published by Pen & Sword Military. Here: British troops hitch a ride on a Mark IV after the massed tank fleet spearheading attack at Cambrai on November 20, 1917. (Photo by Anthony Tucker-Jones/Mediadrumworld.com)

This combination picture shows some revellers wearing masks while dressed as “Botargas” during carnival celebrations in Almiruete, Spain, February 25, 2017. (Photo by Sergio Perez/Reuters)