instruction:
In this task, you are given two strings A, B. Find the longest common substring in the strings A and B.
question:
yrIDSuVuQU, UXTSuVuLcch
answer:
SuVu


question:
OBzHWjmkcgVGPyv, gCHWjmkcgVMq
answer:
HWjmkcgV


question:
slaprCoSjtfyu, YrbprCoSjANTY
answer:

prCoSj