Longest Substring with At Most N Distinct Characters

You are given an integer n and a string s. Your task is to find the length of the longest substring of s that contains at most n distinct characters.

In other words, if a substring contains more than n unique characters, it is not valid. The answer is the maximum possible length of a valid substring.

Mathematically, if we denote by \(f(s, n)\) the length of the longest substring with at most n distinct characters, you need to compute \(f(s, n)\).

Note: If n is 0, or the string is empty, the result is 0.

inputFormat

The input is given via stdin and consists of two lines. The first line contains an integer n. The second line contains the string s.

For example:

2
eceba

outputFormat

Output a single integer representing the length of the longest substring containing at most n distinct characters. The output should be written to stdout.

2
eceba

3