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

SOLUTION: Jn

PROBLEM: eMDNXl, ZZDNAa

SOLUTION: DN

PROBLEM: elXmLYpGCfhzbxNL, TAmpGCfhzbbusfyye

SOLUTION:
pGCfhzb