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

[EX Q]: PnRypl, HvRydi
[EX A]: Ry

[EX Q]: IKrQfT, crrQRg
[EX A]: rQ

[EX Q]: zRzQtDXW, KGNQtDpjN
[EX A]:
QtD