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

Ex Input:
YWNPkA, LuNPnN

Ex Output:
NP


Ex Input:
fVEFJa, WtEFYK

Ex Output:
EF


Ex Input:
ySCGyyXg, KRlGyySv

Ex Output:

Gyy