CF1760B.Atilla's Favorite Problem

In order to write a string, Atilla needs to first learn all letters that are contained in the string.

Atilla needs to write a message which can be represented as a string $s$ . He asks you what is the minimum alphabet size required so that one can write this message.

The alphabet of size $x$ ( $1 \leq x \leq 26$ ) contains only the first $x$ Latin letters. For example an alphabet of size $4$ contains only the characters $\texttt{a}$ , $\texttt{b}$ , $\texttt{c}$ and $\texttt{d}$ .

The first line contains a single integer $t$ ( $1 \leq t \leq 1000$ ) — the number of test cases.

The first line of each test case contains a single integer $n$ ( $1 \leq n \leq 100$ ) — the length of the string.

The second line of each test case contains a string $s$ of length $n$ , consisting of lowercase Latin letters.

For each test case, output a single integer — the minimum alphabet size required to so that Atilla can write his message $s$ .

For the first test case, Atilla needs to know only the character $\texttt{a}$ , so the alphabet of size $1$ which only contains $\texttt{a}$ is enough.

For the second test case, Atilla needs to know the characters $\texttt{d}$ , $\texttt{o}$ , $\texttt{w}$ , $\texttt{n}$ . The smallest alphabet size that contains all of them is $23$ (such alphabet can be represented as the string $\texttt{abcdefghijklmnopqrstuvw}$ ).