Militants loyal to Yemen's exiled government ride on the back of a pick-up truck in the country's central city of Taiz August 19, 2015. Militia forces loyal to Yemen's exiled government fought their way deep into the central city of Taiz this week, local officials said, largely pushing out Houthi militiamen from the country's third largest city. (Photo by Reuters/Stringer)

A passenger without pants waits for the subway train during “The No Pants Subway Ride” in Mexico City January 11, 2015. The event, the fifth organized in Mexico, is an annual flash mob and occurs in different cities around the world, according to its organisers. (Photo by Edgard Garrido/Reuters)

Police officers standby while a forest fire burns the hills of Valparaiso city, northwest of Santiago, March 13, 2015. Several hectares of land has been burned due to forest fires near Valparaiso city, with no report of deaths or injuries, local authorities said. (Photo by Lucas Galvez/Reuters)

A Palestinian youth practices his parkour skills at Shati refugee camp in Gaza City April 27, 2014. (Photo by Mohammed Salem/Reuters)

Dancers rehearse for the Rockettes 2015 Radio City Christmas Spectacular in New York October 15, 2015. (Photo by Lucas Jackson/Reuters)

A girl poses in her costume during a Halloween party at a mall in Quezon city, Metro Manila October 24, 2015. (Photo by Ezra Acayan/Reuters)

A woman has her hair blown by the wind during a snowstorm in Quebec City, on December 22, 2013. (Photo by Mathieu Belanger/Reuters)

People purchase the book “Steve Jobs” by Walter Isaacson on launch day at Shanghai's City of Books on October 24, 2011 in Shanghai, China. The book was launched in 30 book cities at the same time across the country. (Photo by ChinaFotoPress/Getty Images)