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 $\texttt{d}$.

Input

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.

Output

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

见题面 Input 部分

见题面 Output 部分

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 $\texttt{abcdefghijklmnopqrstuvw}$).