Five-year-old Ghazal al-Hussein poses inside a classroom in the rebel-controlled area of Maarshureen village in Idlib province, Syria March 12, 2016. March 15 marks the 5th anniversary of peaceful protests against Syria's President Bashar al-Assad, leading to the devastating civil conflict in the country. These are portraits of five-year-old Syrian children who have only known conflict in their country. (Photo by Khalil Ashawi/Reuters)

A man holds a copy of the Koran during a protest against Niger President Mahamadou Issoufou's attendance last week at a Paris rally in support of French satirical weekly Charlie Hebdo, which featured a cartoon of the Prophet Mohammad as the cover of its first edition since an attack by Islamist gunmen, in Niamey January 17, 2015. (Photo by Tagaza Djibo/Reuters)

An employee of the National Park Service takes a selfie with President Barack Obama, left, in the background meeting with the crowd after a tour of Everglades National Park on Earth Day, Wednesday, April 22, 2015, in Florida. Obama used the visit to warn of the damage that climate change is already inflicting on the nation's environmental treasures. (Photo by Lynne Sladky/AP Photo)

A lone protester sings outside the offices of Republican president-elect Donald Trump at Trump Tower in New York, New York, U.S. November 14, 2016. (Photo by Carlo Allegri/Reuters)

A photograph of Cuba's former President Fidel Castro decorates a wall inside a state-run market in Havana, March 8, 2016. (Photo by Alexandre Meneghini/Reuters)

Children wave Vietnamese and American flags while waiting for arrival of U.S. President Barack Obama (not pictured) before a welcoming ceremony at the Presidential Palace in Hanoi, Vietnam May 23, 2016. (Photo by Reuters/Kham)

Mongolian President Tsakhiagiin Elbegdorj (C) walks towards the media after casting his vote for the parliamentary elections at a polling station in Ulaanbaatar, Mongolia, June 29, 2016. (Photo by Jason Lee/Reuters)

A supporter of China's President Xi Jinping waits on the Mall for him to pass during his ceremonial welcome, in London, Britain, October 20, 2015. Xi is on a State visit to Britain. (Photo by Peter Nicholls/Reuters)