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

[EX Q]: goyZUz, QryZlD
[EX A]: yZ

[EX Q]: lLxXqKscqizXTO, TqrKscqizutDudo
[EX A]: Kscqiz

[EX Q]: agBPYXFiW, YRjMPYXFslGR
[EX A]:
PYXF