In this task you will be given a string and you should find the longest substring that is a palindrome. A palindrome is a string that is the same backwards as it is forwards. If the shortest possible palindrome is length 1 you should return the first character.

Example Input: nqnnffnnnfnq
Example Output: nnffnn

Example Input: xexeexeeexxw
Example Output: exeexe

Example Input: mtmiiimtttmmt
Example Output:
tmiiimt