Four guys are attempting to cross over a chasm on a rickety old bridge
in the middle of the night. Because it is so dark, the bridge can only
be crossed with a lantern. Because the bridge is so unstable, only
two people can cross the bridge at a time.
The guys do have one lantern with them that will allow them to cross,
however, they are not all as nimble as each other. As a result, they
take different lengths of time to cross the bridge. The respective times
it takes for each to cross is 1min, 2min, 5min and 10min.
If two guys are walking across the bridge together with the lantern,
they can only cross as fast as the slower of the two can.
What order should they go in to get all four of the guys
across the bridge in the shortest total amount of time?