B"Let's denote the f(x) function for a string x as the number of distinct characters that the string contains. For example f( texttt{abc}) = 3 , f( texttt{bbbbb}) = 1 , and f( texttt{babacaba}) = 3 . Given a string s , split it into two non-empty strings a and b such that f(a) + f(b) is the maximum possible. In other words, find the maximum possible value of f(a) + f(b) such that a + b = s (the concatenation of string a and string b is equal to string s ). The input consists of multiple test cases. The first line contains an integer t ( 1 <= q t <= q 10^4 ) -- the number of test cases. The description of the test cases follows. The first line of each test case contains an integer n ( 2 <= q n <= q 2 cdot10^5 ) -- the length of the string s . The second line contains the string s , consisting of lowercase English letters. It is guaranteed that the sum of n over all test cases does not exceed 2 cdot10^5 . For each test case, output a single integer -- the maximum possible value of f(a) + f(b) such that a + b = s . For the first test case, there is only one valid way to split texttt{aa} into two non-empty strings texttt{a} and texttt{a} , and f( texttt{a}) + f( texttt{a}) = 1 + 1 = 2 . For the second test case, by splitting texttt{abcabcd} into texttt{abc} and texttt{abcd} we can get the answer of f( texttt{abc}) + f( texttt{abcd}) = 3 + 4 = 7 which is maximum possible. For the third test case, it doesn't matter how we split the string, the answer will always be 2 . "...