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

SOLUTION: CJ

PROBLEM: PzXzvmYrlGZgOBk, iKnzvmYrlGZgOrs

SOLUTION: zvmYrlGZgO

PROBLEM: EDPfAA, WQPfuN

SOLUTION:
Pf