There is a traditional puzzle where 3 missionaries and 3 cannibals have to cross a river using a small canoe. Rules are:
* You cannot have more cannibals than missionaries in either bank because cannibals will eat missionaries.
* The canoe can be run by either one or two persons. Both cannibals and missionaries know how to run it.
This puzzle is really easy to solve either by hand or programming. However, hacking a script to solve it is always more challenging than solving it by hand. Juanjo proposes a solution using Ruby in Misioneros y can