TOPSHOT - US President Barack Obama leaves after an event celebrating the Villanova Wildcats men's basketball 2016 NCAA championship win in the East Room of the White House May 31, 2016 in Washington, DC. / AFP / Brendan Smialowski (Photo credit should read BRENDAN SMIALOWSKI/AFP/Getty Images)
A Syrian man carries his two girls as he walks across the rubble following a barrel bomb attack on the rebel-held neighbourhood of al-Kalasa in the northern Syrian city of Aleppo on September 17, 2015. Once Syria's economic powerhouse, Aleppo has been ravaged by fighting since the rebels seized the east of the city in 2012, confining government forces to the west. AFP PHOTO / KARAM AL-MASRI (Photo credit should read KARAM AL-MASRI/AFP/Getty Images)