instruction:
In this task, you are given two strings A, B. Find the longest common substring in the strings A and B.
question:
egYXVtCPvWxP, VMOolyVtCPvWjIx
answer:
VtCPvW


question:
xtCJGe, DXCJSw
answer:
CJ


question:
mhPPQdcvjRmaFuxvJ, sldcvjRmaFuxCxSn
answer:

dcvjRmaFux