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

[EX Q]: FCKbAgSVgj, wAEAWbAgSVSVwD
[EX A]: bAgSV

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

[EX Q]: oEjQFTubRkYmKiU, LjehjQFTubRWwd
[EX A]:
jQFTubR