instruction:
In this task, you are given two strings A, B. Find the longest common substring in the strings A and B.
question:
ykDpbd, YFDpmO
answer:
Dp


question:
ChKUlYUTQQBjZMZkgEed, lmQQBjZMZkgdEf
answer:
QQBjZMZkg


question:
dQxLKVTSOQHTLpITHLUp, QLifsOQHTLpITHOgYfvO
answer:

OQHTLpITH