instruction:
In this task, you are given two strings A, B. Find the longest common substring in the strings A and B.
question:
zeuyZKwvIOfx, BlmZKwvspUt
answer:
ZKwv


question:
xMxyohPBlJIEBqghiMdBQPwq, xsBlJIEBqghlMosK
answer:
BlJIEBqgh


question:
sVHVSvNVkoxewyE, gPAaavNVkoxekL
answer:

vNVkoxe