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

[EX Q]: HaIPcFXLhYDp, AdIPcFXtJdRE
[EX A]: IPcFX

[EX Q]: bdCOjNchdKtvWzOI, FwejNchdKhEd
[EX A]: jNchdK

[EX Q]: OjOWMKDVqlBjMCWYgpVdrwqfe, UcXOqlBjMCWYgqW
[EX A]:
qlBjMCWYg