Arrange II

You are given a sequence of black and white horses, and a set of K stables numbered 1 to K. You have to accommodate the horses into the stables in such a way that the following conditions are satisfied:

  • You fill the horses into the stables preserving the relative order of horses. For instance, you cannot put horse 1 into stable 2 and horse 2 into stable 1. You have to preserve the ordering of the horses.
  • No stable should be empty and no horse should be left unaccommodated.
  • Take the product (number of white horses * number of black horses) for each stable and take the sum of all these products. This value should be the minimum among all possible accommodation arrangements


Input: {WWWB} , K = 2
Output: 0

We have 3 choices {W, WWB}, {WW, WB}, {WWW, B}
for first choice we will get 1*0 + 2*1 = 2.
for second choice we will get 2*0 + 1*1 = 1.
for third choice we will get 3*0 + 0*1 = 0.

Of the 3 choices, the third choice is the best option. 

If a solution is not possible, then return -1

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