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

SOLUTION: kgLvh

PROBLEM: wrVsKN, mOVsWo

SOLUTION: Vs

PROBLEM: VXwqLjJbjyNf, wILjJbpt

SOLUTION:
LjJb