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

SOLUTION: NnbsUd

PROBLEM: qQkmYsYN, UhkmYHSy

SOLUTION: kmY

PROBLEM: DkJkONPtfQutldsn, NunlXmONPtfQYFpzLO

SOLUTION:
ONPtfQ