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

Q: IGHhMfqLeBpnullsPInfBH, LTDBpnullsPIBynwCrCQ

A: BpnullsPI
****
Q: EPUxsZtt, KgxsZuXM

A: xsZ
****
Q: WIMtNNsjzrKYrJObpe, elMtNNsjzrKbG

A:
MtNNsjzrK
****