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

Q: vMsEJRoLkWcmkuwNRz, ZmoLkWcmVZiBv

A: oLkWcm
****
Q: rCFrfkmXbSHK, mztfkmXwez

A: fkmX
****
Q: CveXOnKaqzFr, LgOnKakbW

A:
OnKa
****