A11215. 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 $a_{1}<j<a_{2}$ for some $a_{1}$ and $a_{2}$ from $A$ ).

Write a program that will determine the maximum number of elements in a pretty set of positions.

The first line contains a single integer $n$ ( $1<=n<=200$ ) — length of string $s$ .

The second line contains a string $s$ consisting of lowercase and uppercase Latin letters.

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 $0$ .