AT_agc078_a [AGC078A] Rearrange ABC

You are given strings $ S $ and $ T $ of length $ 3N $ , each containing exactly $ N $ occurrences of each of `A`, `B`, and `C`. You can perform the following operation zero or more times. - Choose one substring of $ S $ whose characters are all distinct. - Sort the characters of the chosen substring in ascending order. Determine whether it is possible to make $ S $ equal to $ T $ , and if it is possible, find the minimum number of operations required.

The input is given from Standard Input in the following format: > $ N $ $ S $ $ T $

Output the answer. If it is impossible to make $ S $ equal to $ T $ , output `-1`.

### Sample Explanation 1 For example, you can make $ S $ equal to $ T $ by performing two operations as follows. - Choose the first two characters of `CACBAB`, making it `ACCBAB`. - Choose the $ 3 $ -rd through $ 5 $ -th characters of `ACCBAB`, making it `ACABCB`. It is impossible to make them equal with one operation, so the answer is $ 2 $ . ### Sample Explanation 2 No matter how you perform the operations, you cannot make `ABC` equal to `CBA`. ### Constraints - $ 1 \le N \le 100 $ - $ S $ and $ T $ are strings of length $ 3N $ consisting of `A`, `B`, and `C`. - Each of $ S $ and $ T $ contains exactly $ N $ occurrences of each of `A`, `B`, and `C`. - All input values are integers.