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

SOLUTION: RUmI

PROBLEM: cxYVucnmEQopeWHrPJ, jNnOaYVucnmEQoSE

SOLUTION: YVucnmEQo

PROBLEM: xXZQKsjRWgRFEr, iGAQKsjRWkIsWEF

SOLUTION:
QKsjRW