[Pope Francis waves as he boards a plane at Fiumicino Airport in Rome]Pope Francis met U.S. presidential candidate Bernie Sanders on Saturday morning before leaving for a visit to the Greek island of Lesbos, a participant at the meeting said. Columbia University Professor Jeffrey Sachs told Reuters that the meeting took place in the Vatican guesthouse where the pope lives and where Sanders had spent the night after addressing a Vatican conference on social justice. Sachs said Sanders, who was accompanied by his wife, and the pope spoke for about five minutes.