using System;

using System.Collections.Generic;                   

public class Program

{

    public static void Main()

    {

        Console.WriteLine(MaxFruitCountOfk(new Char[]{'A', 'B', 'C', 'A', 'C'}, 2));

        Console.WriteLine(MaxFruitCountOfk(new Char[]{'A', 'B', 'C', 'B', 'B', 'C'}, 2));

    }

    public static int MaxFruitCountOfk(char[] arr, int k)

    {

        var windowStart = 0;

        var maxLength = 0;

        var hashMap = new Dictionary<char, int>();

        for(var windowEnd = 0; windowEnd < arr.Length; windowEnd++)

        {

            var rightChar = arr[windowEnd];

            if(hashMap.ContainsKey(rightChar))

            {

                hashMap[rightChar] ++;

            }

            else 

            {

                hashMap.Add(rightChar, 1);

            }

            while(hashMap.Count > k)

            {

                var leftChar = arr[windowStart];

                hashMap[leftChar]--;

                if(hashMap[leftChar] == 0)

                {

                    hashMap.Remove(leftChar);

                }

                windowStart++;

            }

            maxLength = Math.Max(maxLength, windowEnd - windowStart + 1);

        }

        return maxLength;

    }

}