Example. Consider the following problem (with no attempted biological motivation.) Given: A set of n positive numbers. Desired output: Divide the numbers into two sets, where the difference between the sums of the sets is as small as possible. (Given a set of blocks of different heights, put them into two piles that are as close as possible to the same height.) Devise a greedy method that attempts to find a solution, and find an instance where it gives a sub-optimal solution.