TASK DEFINITION: In this task, you are given two strings A, B. Find the longest common substring in the strings A and B.
PROBLEM: ZRjPgqbLL, uIsmPgqbBB

SOLUTION: Pgqb

PROBLEM: wCfNCfxvLRAxBstRTwMSqTn, AhwxfFNCfxvLRAxBrNtf

SOLUTION: NCfxvLRAxB

PROBLEM: rkCqYzaMNzkAYyxKzoVRY, rKhcYNOMNzkAYyxuPE

SOLUTION:
MNzkAYyx