CF864B Polycarp and Letters

Polycarp loves lowercase letters and dislikes uppercase ones. Once he got a string $ s $ consisting only of lowercase and uppercase Latin letters. Let $ A $ be a set of positions in the string. Let's call it pretty if following conditions are met: - letters on positions from $ A $ in the string are all distinct and lowercase; - there are no uppercase letters in the string which are situated between positions from $ A $ (i.e. there is no such $ j $ that $ s[j] $ is an uppercase letter, and $ a_{1}

The first line contains a single integer $ n $ ( $ 1

Print maximum number of elements in pretty set of positions for string $ s $ .

In the first example the desired positions might be $ 6 $ and $ 8 $ or $ 7 $ and $ 8 $ . Positions $ 6 $ and $ 7 $ contain letters 'a', position $ 8 $ contains letter 'b'. The pair of positions $ 1 $ and $ 8 $ is not suitable because there is an uppercase letter 'B' between these position. In the second example desired positions can be $ 7 $ , $ 8 $ and $ 11 $ . There are other ways to choose pretty set consisting of three elements. In the third example the given string $ s $ does not contain any lowercase letters, so the answer is $ 0 $ .