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

[EX Q]: ARGchkRez, kUwchkZPE
[EX A]: chk

[EX Q]: qczzCr, zDzzUI
[EX A]: zz

[EX Q]: aelhyxDJiHgTcduHBOKsFfJH, LupBVcJiHgTcduHtnTBNBLGq
[EX A]:
JiHgTcduH