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:
kvutZfcPKzHE, kTKutZfcPTGmU

Ex Output:
utZfcP


Ex Input:
yvHImG, otHIfu

Ex Output:

HI