instruction:
In this task, you are given two strings A, B. Find the longest common substring in the strings A and B.
question:
XeQwOS, OuQwNR
answer:
Qw


question:
JjEQVKijeyEQ, dwSVKijeywCTvb
answer:
VKijey


question:
dQWktpVdfqUOvKS, FIcxatpVdfqCr
answer:

tpVdfq