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

Q: FiKGCRXutEOzMqP, xdxRXutEsl

A: RXutE
****
Q: XjYkMfARxWBSBjuXyDrFt, EtUxIfiHkMfARxWBSckTLTTnR

A: kMfARxWBS
****
Q: hYRJgV, ikRJBw

A:
RJ
****