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

SOLUTION: pBHsrf

PROBLEM: mQvintdwLUpClREgxv, rYnoXBtdwLUpClRwxsqX

SOLUTION: tdwLUpClR

PROBLEM: RangRoKieSsFkvBExtQ, gXnEGNgRoKieSsVDwHwpdC

SOLUTION:
gRoKieSs