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

SOLUTION: toQ

PROBLEM: ljwjMioOwfOltGBaE, TneNGsoOwfOlxnWWW

SOLUTION: oOwfOl

PROBLEM: BtPNncc, GoPNnmLd

SOLUTION:
PNn