Make It A Subsequence

You are given two case-sensitive strings: firstString and secondString. You may remove characters from secondString. The remaining characters must stay in their original order. Your goal is to make the remaining secondString a subsequence of firstString. If you remove no characters, the cost is 0. Otherwise, suppose the removed characters originally had indices from L to R in secondString. The cost is: R - L + 1 Return the minimum possible cost. Since removing extra characters between L and R never increases the cost, the task can be viewed as removing one contiguous window from secondString so that the remaining prefix and suffix together form a subsequence of firstString.