In this task, you are given two strings A, B. Find the longest common substring in the strings A and B.

Q: xfZYYDKEqoRRu, ztCeYYDKEqoPG

A: YYDKEqo
****
Q: goyZUz, QryZlD

A: yZ
****
Q: LkKBHK, nYKBij

A:
KB
****