instruction:
In this task, you are given two strings A, B. Find the longest common substring in the strings A and B.
question:
HaIPcFXLhYDp, AdIPcFXtJdRE
answer:
IPcFX


question:
lOedgdw, aoedgpn
answer:
edg


question:
AKFkpc, FIFkIE
answer:

Fk