We have a string s of length n, which contains only UPPERCASE characters and we have a number k (always less than n). We can make at most k changes in our string. In one change, you can replace any s[i] (0<= i < n) with any uppercase character (from 'A' to 'Z'). After k changes, find the maximum possible length of the sub-string which have all same characters.

Example 1:

Input: s = "ABAB", k = 2
Output: 4
Explanation: Change 2 'B' into 'A'. 
Now s = "AAAA"

Example:

Input: s = "ADBD", k = 1
Output: 3
Explanation: Change 'B' into 'D'.
Now s = "ADDD"

Your Task:
You don't need to read or print anything. Your task is to complete the function characterReplacement() which takes s and k as input parameters and returns the maximum length of sub-string after doing k changes.

Expected Time Complexity: O(n)
Expected Space Complexity: O(26)

Constraints:
1 <= n <= 10⁵
0 <= k < n