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

SOLUTION: YuZvA

PROBLEM: yxJxNRLEnKGHziJtfb, KfReWhEnKGHzitzfPWzK

SOLUTION: EnKGHzi

PROBLEM: WXDXfNQQm, BMGbDXfNxq

SOLUTION:
DXfN