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

Ex Input:
UtUSmsOI, dCUSmGoQ

Ex Output:
USm

Ex Input:
bOvlVNWf, iivlVzWt

Ex Output:
vlV

Ex Input:
EoOSeDBlTiCepJocb, tQKBzDBlTiCepJolNAJWSB

Ex Output:
DBlTiCepJo