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

Ex Input:
WFAPUCgVYbmZiFlacUzyv, xQFiekrgPUCgVYbmZUEtl

Ex Output:
PUCgVYbmZ


Ex Input:
yJRITYgVTSNsPjG, NSIdKYgVTSNmj

Ex Output:
YgVTSN


Ex Input:
QxtmksxHbGJS, uSqZFltmksxHpp

Ex Output:

tmksxH