Kitty

Cats are so cute. People adored cats so much that they decided to build a cat language translator to communicate with them. This translator will turn human language into cat language and cat language into human language, an invention unlike any other.

A beta version of the cat language translator is out now. But this beta is a complete mess. Given a string, the beta translator recognizes only a contiguous substring that contains at most N distinct letters. It is a poor showing, but people thought it was the best they could do. They also want to know the length of the longest substring this translator can recognize for a given string.

Let us work together so we can communicate with cats.

The first line contains N, the maximum number of distinct letters the translator can recognize. (1 < N ≤ 26)

The second line contains a string. (1 ≤ length of the string ≤ 100,000) The string contains only lowercase English letters.

Print the maximum length of a string the translator can recognize.

For abbcaccba, the answer is cacc. The translator recognizes at most 2 distinct letters, and the longest contiguous substring with at most 2 distinct letters is cacc. So the answer is the length of cacc, which is 4.