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

Q: rCFrfkmXbSHK, mztfkmXwez

A: fkmX
****
Q: HEVqGddewrNqiZ, iyvlddewrNXr

A: ddewrN
****
Q: EErOXd, YgrOQJ

A:
rO
****