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

[EX Q]: ilgSzrcUKLTNLJbMKMKSt, hFXIuUKLTNLJbMKWxSCkDjY
[EX A]: UKLTNLJbMK

[EX Q]: YXsgPE, ENsgSO
[EX A]: sg

[EX Q]: KiPQEwCXTtMYaslhPMFiX, ejiqGruPQEwCXTtMYDe
[EX A]:
PQEwCXTtMY