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

Ex Input:
MriFNpGM, yaiFNduk

Ex Output:
iFN


Ex Input:
jXbgnl, lUbglP

Ex Output:
bg


Ex Input:
BTvLVMYp, mjOvLVMqYo

Ex Output:

vLVM