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

SOLUTION: YYDKEqo

PROBLEM: XHqQIPw, brqQIkAt

SOLUTION: qQI

PROBLEM: xpbFAmBFXe, VUXmFAmBET

SOLUTION:
FAmB