Obama says ready to train new leaders in first post-presidency speech

After three months off, Obama -- looking rested and sporting a coat with no tie -- broke his silence in his adopted hometown of Chicago, speaking to a packed auditorium of more than 400 high school and college students at the University of Chicago.The 55-year-old Democrat, who ended his two terms at the White House in January -- handing power over to Donald Trump -- said he was "incredibly optimistic" about the future."I'm spending a lot of time thinking about: what is the most important thing I