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]: lrBJDRkT, jmBJDrI
[EX A]: BJD

[EX Q]: mIRsvalT, CSRsvaALYd
[EX A]:
Rsva