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

SOLUTION: KtWU

PROBLEM: STvKOHq, XMGvKOdyM

SOLUTION: vKO

PROBLEM: zfUPUDeKbCMQa, BkAJFJUDeKbCMZmkFu

SOLUTION:
UDeKbCM