instruction:
In this task, you are given two strings A, B. Find the longest common substring in the strings A and B.
question:
AuSFmN, crSFXM
answer:
SF


question:
wXGerDNhSNnCCedyzskswVnh, BfFNhSNnCCedybrUbI
answer:
NhSNnCCedy


question:
guhvOWokGsPk, fPOWokbjJ
answer:

OWok