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:
IIbJjQKWaoGKHGgWPcy, uNoMWaoGKHGqbnjmYQ
answer:
WaoGKHG


question:
XryNdJRrzpslklKEY, MQeRrzpslRU
answer:

Rrzpsl