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

[EX Q]: spUbdWDLWCeqr, vIuHkWDLWCQEPaz
[EX A]: WDLWC

[EX Q]: mCxQTIaXN, mWQTIaxzPT
[EX A]: QTIa

[EX Q]: NiqXPBN, QUqXPZqN
[EX A]:
qXP