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]: XbjDHRCWxdPbhibUKn, SrpuPDHRCWxdPbKPWEXNWbZ
[EX A]: DHRCWxdPb

[EX Q]: zyPuckXGZLHd, uKickXGVXn
[EX A]:
ckXG