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: koIZvrJmfKCO, TBvrtjcWIZvrJmfKRZDOE

SOLUTION: IZvrJmfK

PROBLEM: bDopoiGDMcbkEIYVJIfH, PTFmTCLoiGDMcbkmcIWonzj

SOLUTION:
oiGDMcbk