There is a river and on one side of the river bank there are three Lions and three wilder-beasts and they all have to cross the river...from left to right
to get across there is a small boat that can fit two animals...
thus the boat can be manned by one animal or two...
unfortunately lions being lions they will eat the wilder-beasts if at any point the number of lions on their side of the bank exceeds the number of wilder-beasts
(so if two wilder-beasts cross then on the left bank there is three lions and one wilder-beast thus lions will eat the wilder-beast)
how does all the animals cross the river? and how many trips do they take (or rather what is the shortest amount of trips for all animals to safely cross)