Maximum Beauty of a Substring

Given a string s of length n, your task is to determine the maximum beauty among all possible substrings of s. The beauty of a substring is defined as the number of distinct characters it contains. Formally, for a substring S, its beauty is given by:

$$ B(S) = \left| \{ c : c \text{ appears in } S \} \right| $$

Print the maximum beauty value that can be achieved by any substring of s.

inputFormat

The first line contains an integer n — the length of the string.

The second line contains a string s consisting of n lowercase English letters.

outputFormat

Output a single integer — the maximum beauty among all substrings of s.

## sample

7
abcabc

3

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