instruction:
In this task, you are given two strings A, B. Find the longest common substring in the strings A and B.
question:
MriFNpGM, yaiFNduk
answer:
iFN


question:
DFRoMPNDAzNgtLsEPseOzC, qykyPjDAzNgtLsEPYTsNrJaNK
answer:
DAzNgtLsEP


question:
tNkJLBEl, pyVkJLvDh
answer:

kJL