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

[EX Q]: BrDGrTD, PBHDGrDw
[EX A]: DGr

[EX Q]: eJPZzg, lFPZbI
[EX A]: PZ

[EX Q]: IxeFUEqCrBf, BwQyeFUEqCNJ
[EX A]:
eFUEqC