Detailed Instructions: In this task, you are given two strings A, B. Find the longest common substring in the strings A and B.
See one example below:
Problem: PPdQTlHHTJEe, DydQTlHHVnmlLu
Solution: dQTlHH
Explanation: Here, 'dQTlHH' is the longest common substring in both the input strings 'PPdQTlHHTJEe' and 'DydQTlHHVnmlLu'.

Problem: ZSuMua, CtuMlX
Solution:
uM