Taco: Minimize Distinct Characters

Given a positive integer n and a string s of length n, your task is to determine the minimum number of distinct characters in the string after performing the transformation. In other words, compute the number of unique characters in s. This can be mathematically expressed as: $$ answer = \left|\{ s_i : s_i \in s \}\right| $$

You will be given multiple test cases; for each test case, output the result on a new line.

inputFormat

The first line contains a single integer T which denotes the number of test cases. Each test case consists of a single line containing an integer n and a string s (with exactly n characters) separated by space.

outputFormat

For each test case, output a single integer representing the number of distinct characters in s.

3
6 aabbcc
4 abcd
7 abcdeaa

3
4
5