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

[EX Q]: GrvtMjEvRlmN, ifGOWMjEvRPSOZK
[EX A]: MjEvR

[EX Q]: ScUCglVzZFPjLVofNHOumU, mNodEXwpZFPjLVofYfSnBM
[EX A]: ZFPjLVof

[EX Q]: OjQHcFUCflYUptUPqYKVomn, GXHcFUCflYUpSSTrQ
[EX A]:
HcFUCflYUp