B. Atilla's Favorite Problemtime limit per test1 secondmemory limit per test256 megabytesinputstandard inputoutputstandard outputIn 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}.InputThe 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.OutputFor each test case, output a single integer — the minimum alphabet size required to so that Atilla can write his message s.ExampleInput
51a4down10codeforces3bcf5zzzzzOutput
1
23
19
6
26
NoteFor 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}).
51a4down10codeforces3bcf5zzzzz
1 23 19 6 26 
['greedy', 'implementation', 'strings', '*800']