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

Example input: PPdQTlHHTJEe, DydQTlHHVnmlLu
Example output: dQTlHH
Example explanation: Here, 'dQTlHH' is the longest common substring in both the input strings 'PPdQTlHHTJEe' and 'DydQTlHHVnmlLu'.
Q: TEXePoLvYpfsEkl, DSoLvYpfOzGzR
A:
oLvYpf