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

SOLUTION: VlCwpfO

PROBLEM: PIcbiJj, hedcbiZHF

SOLUTION: cbi

PROBLEM: rIvQwcfKhHZ, rtFMwcfKhjGxJV

SOLUTION:
wcfKh