In this task, you are given two strings A, B. Find the longest common substring in the strings A and B.

Example Input: haOsaSQcyodWhqQaC, BKLEUQcyodWhvVkmxBz
Example Output: QcyodWh

Example Input: aeQjEeiWGONmzGimhGiw, RIEeiWGONmOZuVYr
Example Output: EeiWGONm

Example Input: rZFfcCYjgf, YkpcCYjYbrK
Example Output:
cCYj

