During certain local floods five married couples found themselves
surrounded by water, and had to escape from their unpleasant position in
a boat that would only hold three persons at a time. Every husband was
so jealous that he would not allow his wife to be in the boat or on
either bank with another man (or with other men) unless he was himself
present. Show the quickest way of getting these five men and their wives
across into safety.
Call the men A, B, C, D, E, and their respective wives a, b, c, d, e. To
go over and return counts as two crossings. No tricks such as ropes,
swimming, currents, etc., are permitted.