we thank you, carolyn ryan with the "new york times." jon meacham.nk you, all three of you. >> woodruff: online, we give you the chance to watch and interact with every presidential debate since 1960 at watch the debates dot org. >> woodruff: as we reported earlier, 21 of nigeria's so- called chibok girls, kidnapped by the militant group boko haram, were released today. but there is a larger and more far-reaching menace lurking in the war-torn reaches of that country: hunger. aid groups warn of a coming famine. john yang has our look. a warning: the story contains some graphic images. >> yang: there is a calamity-in- the making in nigeria's northeastern borno state. that's the territory where government forces have been fighting boko haram for years. caught in the middle: as many as three million nigerians, who, aid groups say, are in danger of starving. it is also where those chibok girls were kidnapped in 2014. "washington post" correspondent kevin sieff just completed a reporting trip there, and joins us from nairobi, kenya. kevin, you write this