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

[EX Q]: OyXwTWbLByC, yODnTWbLWYzc
[EX A]: TWbL

[EX Q]: lMRuEThD, wqQRuEKp
[EX A]: RuE

[EX Q]: GBqnCB, wsqnLf
[EX A]:
qn