instruction:
In this task, you are given two strings A, B. Find the longest common substring in the strings A and B.
question:
hUpEbyvEcQ, dHpEbyvEvwsXcN
answer:
pEbyvE


question:
PGjDRPDzGaBR, rpIJRPDzWi
answer:
RPDz


question:
MrYmrRBaCcbOsNeuPNtSKEL, XvemrRBaCcbOsjtI
answer:

mrRBaCcbOs