Minimum Operations to Rearrange Books

Given an initial arrangement of books and a desired target order, determine the minimum number of reversal operations required to transform the initial sequence into the target sequence. In one reversal operation, you may select any contiguous segment of the books and reverse its order.

For example, if the initial arrangement is abcd and the target arrangement is dcba, one reversal of the entire sequence will achieve the target order.

The problem can be formalized as: Given strings \(B\) (for books) and \(T\) (for target), find the minimum \(k\) such that after performing exactly \(k\) reversal operations, the arrangement equals \(T\). In formula form, $$ \text{operations} = \min\{ k \mid R(k) = T \}, $$ where \(R(k)\) denotes the resultant arrangement after \(k\) reversals.

inputFormat

Standard input consists of two lines. The first line contains a string representing the initial arrangement of books. The second line contains a string representing the desired arrangement of books.

outputFormat

Standard output should contain a single integer representing the minimum number of reversal operations required to rearrange the books into the desired order.## sample

abcd
dcba

1