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

Example Input: apGMPThLTCw, LvMPThYW
Example Output: MPTh

Example Input: jyJrDIhxJtWbnooEXZ, uyXifNCIhxJtWbnVCUrt
Example Output: IhxJtWbn

Example Input: AjVNIV, niVNsj
Example Output:
VN