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

[EX Q]: zeuyZKwvIOfx, BlmZKwvspUt
[EX A]: ZKwv

[EX Q]: rRmkmETbjzCzZZxihrVdefxfcenJ, ogQtzAgWjKCzZZxihrVdRswMCmngp
[EX A]: CzZZxihrVd

[EX Q]: YrlkFEnxmZDvlYvts, SfjlkFEnxmZjAAtwLP
[EX A]:
lkFEnxmZ