Statement

Luca is giving a Christmas gift to each of his N friends! When the presents will be opened in the Giftsgiving Ceremony, his friends will be aligned in a row, numbered from 0 to N-1, and friend i will receive a gift of well-known value V_i. Luca knows that his friends will be able to see other presents at a distance up to K positions (that is, K-1 people in between). Of course, the friends whose gifts are less valuable will be sad: more precisely, their sadness will be equal to the absolute difference between the maximum value of a present they can see and the value of their one. Help Luca prepare for the ceremony by computing how sad will be the saddest friend!