instruction:
In this task, you are given two strings A, B. Find the longest common substring in the strings A and B.
question:
zfUPUDeKbCMQa, BkAJFJUDeKbCMZmkFu
answer:
UDeKbCM


question:
eJPZzg, lFPZbI
answer:
PZ


question:
zyoTANvNlQwRfFM, OcuEDYFNvNlQwRfwpqVv
answer:

NvNlQwRf