Given a string S, find the longest palindromic substring in S. Substring of string S: S[ i . . . . j ] where 0 ≤ i ≤ j < len(S). Palindrome string: A string which reads the same backwards. More formally, S is palindrome if reverse(S) = S. Incase of conflict, return the substring which occurs first ( with the least starting index ).

Example 1:

Input:
S = "aaaabbaa"
Output:
aabbaa
Explanation:
The longest palindrome string present in
the given string is "aabbaa".

Your Task:  
You don't need to read input or print anything. Your task is to complete the function longestPalindrome() which takes string S as input parameters and returns longest pallindrome present in string.

Expected Time Complexity: O(|S|²)
Expected Auxiliary Space: O(1)

Constraints:
1 ≤ |S| ≤ 10⁴