Minimum Balanced Substring Length

Given a string s and an integer k, you are required to find the minimum length of a contiguous substring of s that is balanced. A substring is considered balanced if each letter among the first k lowercase English letters (i.e., from a to the kth letter) appears the same number of times.

If no such substring exists, output -1.

Note: A balanced substring must have a total length that is a multiple of k. In many cases the minimum balanced substring will be one where each of the required letters appears exactly once.

inputFormat

The first line contains an integer t denoting the number of test cases.

Each test case consists of two lines:

• The first line contains an integer k.
• The second line contains a string s consisting only of lowercase English letters.

outputFormat

For each test case, output the minimum length of a balanced contiguous substring. If no balanced substring exists, output -1. Each answer should be printed on a new line.

## sample

6
2
abba
3
abcabc
2
xyz
1
a
2
aaaaabbbbbb
26
abcdefghijklmnopqrstuvwxyz

2
3
-1
1
2
26

</p>