instruction:
In this task, you are given two strings A, B. Find the longest common substring in the strings A and B.
question:
jeQzwP, kSQzxq
answer:
Qz


question:
iaXeqfIrYKxPJRXxfSm, rIYKxPJRXxfsjVsqe
answer:
YKxPJRXxf


question:
gArFCSUFwukMPyifr, NagpCSUFwukMTthD
answer:

CSUFwukM