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

[EX Q]: CdRbREFMEDTXnEzgn, zHLEMMEDTXnEPH
[EX A]: MEDTXnE

[EX Q]: egYXVtCPvWxP, VMOolyVtCPvWjIx
[EX A]: VtCPvW

[EX Q]: AdQUehXuh, IyyUehcZ
[EX A]:
Ueh