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

Example Input: njzfcapS, JDzfcYQh
Example Output: zfc

Example Input: UmYbssMbmsXkKQuzNasLOib, EMqlbmsXkKQuzNcyHrpZXOQW
Example Output: bmsXkKQuzN

Example Input: XHTzKTbAWitB, XiWYvTbAWirJVq
Example Output:
TbAWi