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

[EX Q]: esIMEOgV, tNIMEybb
[EX A]: IME

[EX Q]: BICndZkjoSidWivWATvtqsS, FzVWjoSidWivFaQhkRT
[EX A]: joSidWiv

[EX Q]: UWHuqKQQSlLA, YhqKQQSlmIrdOi
[EX A]:
qKQQSl