Write a class Shark that extends the Critter class from the Critters assignment. Shark objects should alternate between moving to the north and south as follows: first move 1 step north, then 2 steps south, then 3 steps north, then 4 steps south, then 5 steps north, then 6 steps south, and so on, each time moving one farther than previously. You may add anything needed (fields, other methods, constructors, etc.) to implement this behavior appropriately.