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

[EX Q]: ktABEFESAVHZkkY, uMjxiESAVHZkZgWUte
[EX A]: ESAVHZk

[EX Q]: cZSEmdgP, YsSEmEIM
[EX A]: SEm

[EX Q]: SUgXyznbUQRpiLUTlRb, jlnwLTnbUQRpioUFyJ
[EX A]:
nbUQRpi