You are given two Strings A and B that have the same length and contain only lowercase letters ('a'-'z'). The distance between two letters is defined as the absolute value of their difference. The distance between A and B is defined as the sum of the differences between each letter in A and the letter in B at the same position. For example, the distance between "abcd" and "bcda" is 6 (1 + 1 + 1 + 3).
You must change exactly K characters in A into other lowercase letters. Return the minimum possible distance between A and B after you perform that change.