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

[EX Q]: YXsgPE, ENsgSO
[EX A]: sg

[EX Q]: fVEFJa, WtEFYK
[EX A]: EF

[EX Q]: DfvIChDRRwaBbJunXIXiFuX, mEUQhQsopDRRwaBbJurAoH
[EX A]:
DRRwaBbJu

