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

Ex Input:
wnIFoRQvMMKMAqpCQYncuWUTJs, bPMUKKxYRxQvMMKMAqpCmzAPPMD

Ex Output:
QvMMKMAqpC


Ex Input:
uDaqoOpUtLDdTGTO, ncIgBjDPqoOpUtLDdTNtiEyarDO

Ex Output:
qoOpUtLDdT


Ex Input:
sFffEL, vVffXP

Ex Output:

ff