BEIRUT (AP) — As government troops close in on Aleppo, some residents are preparing to flee Syria's largest city while others are hoarding food in case of a long siege, even laying out bread on rooftops to dry it out for storage. The U.N. warned Tuesday that hundreds of thousands of people could be cut off from humanitarian aid as siege conditions tighten around the rebel-controlled eastern part of the city. The city has been divided since 2012, with the government controlling the western portion, while the eastern part is held by insurgents. A government offensive in the countryside north of Aleppo has cut a vital opposition supply route from the Turkish border, leaving just one corridor from the east to the outside world. The U.N.