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

Example Input: jyJrDIhxJtWbnooEXZ, uyXifNCIhxJtWbnVCUrt
Example Output: IhxJtWbn

Example Input: gfXPLNzsyfEotmHL, oJeXPLNzsyJuXP
Example Output: XPLNzsy

Example Input: JmtPHpukIQJjuc, whPHpukIaRnJh
Example Output:
PHpukI

