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

[EX Q]: HqaOvLaZbs, RifOvLaZkh
[EX A]: OvLaZ

[EX Q]: UIjAMFDuxDDGkfQa, VdsHuxDDGkfZHZZ
[EX A]: uxDDGkf

[EX Q]: rSzpTo, XbzpsU
[EX A]:
zp