instruction:
In this task, you are given two strings A, B. Find the longest common substring in the strings A and B.
question:
WFAPUCgVYbmZiFlacUzyv, xQFiekrgPUCgVYbmZUEtl
answer:
PUCgVYbmZ


question:
sRTQgRgRUjEooapKdR, vzsBgRUjEooLBkYeH
answer:
gRUjEoo


question:
QFWEBegyNfRrpHNU, imEBegyNfSpRpv
answer:

EBegyNf