Walkers cross the river Waalbrug during the first day of the 98th annual four-days walking event, the “Vierdaagse” in Nijmegen, Netherlands, July 15, 2014. The “Nijmeegse Vierdaagse” is an annual public four-day field march which is held since 1909 in the third week of July. (Photo by Erik van 't Wout/EPA)

Chinese women wear face-kinis as they walk in to the water to swim at the beach on August 20, 2014 in the Yellow Sea in Qingdao, China. The locally designed mask is worn by many local women to protect them from jellyfish stings, algae and the sun's ultraviolet rays. (Photo by Kevin Frayer/Getty Images)

A visitor walks on a giant chalk artwork called “Wasting Time” at the Chalk Urban Arts Festival in Sydney on October 25, 2014. The picture is the biggest 3-D artwork created in Australia by two artists, Leon Keer from Holland and Jenny McCracken from Australia. (Photo by Peter Parks/AFP Photo)

Labourers walk near trucks loaded with logs, which are trapped on a muddy road, near an unreserved forest in the village of Igbatoro, southwest Nigeria, August 28, 2014. Wood, a form of biomass, is the sole source of energy for hundreds of millions of Africans who lack access to modern sources of power, and logging, both legal and illegal, remains a lucrative business that has contributed to the rapid shrinking of Africa's rainforests and woodlands. (Photo by Akintunde Akinleye/Reuters)

Participants of the the goth festival “Wave Gothic Festival” walk in fancy costumes along the festival area in Leipzig, central Germany, Saturday, May 23, 2015. About 20,000 members of the scene are expected to attend one of the world's largest gothic and “dark” culture festivals until May 25, 2015. (Photo by Jens Meyer/AP Photo)

Tibetan pilgrims walk outside the Sera Monastery in Lhasa, Tibet Autonomous Region, China, 11 September 2016. Sera Monastery is known as one of the “great three” Gelug university monasteries of Tibet founded in 1419. (Photo by How Hwee Young/EPA)

A youth in make-up waits for the start of the annual Zombie walk in Mexico City, Saturday, October 22, 2016. Hundreds dressed in rags and ghoulish makeup to look bloody and decaying, gathered in the historic center of Mexico's capital. (Photo by Christian Palma/AP Photo)

A child walks to an installation made from fallen leaves by college students, in shape of a sofa, to call for people's attention to environment protection, in Hangzhou, Zhejiang province, China, December 6, 2016. (Photo by Reuters/China Daily)