In this task, you are given two strings A, B. Find the longest common substring in the strings A and B.

Q: uDaqoOpUtLDdTGTO, ncIgBjDPqoOpUtLDdTNtiEyarDO

A: qoOpUtLDdT
****
Q: EyvnjbVLF, vqnjblzR

A: njb
****
Q: YbYHXq, ZkYHZu

A:
YH
****