instruction:
In this task, you are given two strings A, B. Find the longest common substring in the strings A and B.
question:
wNiHcaiUPHnjp, aSTmjcaiUPHFzOu
answer:
caiUPH


question:
wnIFoRQvMMKMAqpCQYncuWUTJs, bPMUKKxYRxQvMMKMAqpCmzAPPMD
answer:
QvMMKMAqpC


question:
yxWeRPbQmx, IbURPbQqq
answer:

RPbQ