Damaged buildings stand in the rebel-controlled area of Maaret al-Numan in Idlib province, Syria September 6, 2016. (Photo by Ammar Abdullah/Reuters)

Bull riders prepare prior to a bull riding event in Santa Tecla, El Salvador, December 15, 2016. (Photo by Jose Cabezas/Reuters)

Women pose for a picture at the entrance of the Carlton Hotel, in the government controlled area of Aleppo, Syria December 17, 2016. (Photo by Omar Sanadiki/Reuters)

Convention goers dressed as bright colored Wookiees, a fictional species from the US epic space opera franchise Star Wars, prepare for a group photo outside the Comic Con 2016 in San Diego, California, USA, 22 July 2016. The San Diego Comic Con 2016 runs from 21 until 24 July. (Photo by David Maung/EPA)

An undated handout image provided by UNICEF Germany on 20 December 2016 shows the “UNICEF Photo of the Year 2016” by Iranian freelance photographer Arez Ghaderi. Ghaderi won the first prize for his picture of a girl in a makeshift tent city in the Razavi Khorasan province, Iran, it was announced at a ceremony in Berlin, Germany on 20 December 2016. (Photo by Ariz Ghaderi/EPA/UNICEF Deutschland)

Revellers attend the Play Time 2016 music festival on the outskirts of Ulaanbaatar, Mongolia, June 26, 2016. (Photo by Jason Lee/Reuters)

A barn painted with the U.S. flag is seen in the snow covered field in Kanawha, Iowa, United States, January 16, 2016. Iowa will be the first state to hold its primary, with both Democratic and Republican events being held February 1, 2016. (Photo by Jim Young/Reuters)

An artist performs with a lion during the presentation of the new international show “Extreme arena” at the Ukrainian National Circus in Kiev, Ukraine, 15 September 2016. The show will be staged from 15 September to 11 December 2016. (Photo by Roman Pilipey/EPA)