Late one night, four weary travelers come to an old rickety rope bridge over an crocodile infested gorge. With planks missing here and there, it is not safe to cross without the group's lone flashlight. Also, the bridge does not appear to be able to support more than two people at a time.
The four travelers (oddly named John, Paul, George, and Ringo) each have a varying level of mobility. John can cross in 1 minute, Paul needs 2 minutes, George needs 5 minutes, and Ringo cannot cross in less than 10 minutes. Of course when two travelers cross the bridge, they must travel at the pace of the slower of the two.
With a horde of bloodthirsty fans not far behind the travelers, what is the shortest amount of time needed to cross the bridge? How do they do it?