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

Ex Input:
DGvUCrUVlUnQBShkWnfnceGasvI, NfzGUnQBShkWnpLMnY

Ex Output:
UnQBShkWn


Ex Input:
yQCDWefwvrPP, RwoMDWefwhSxTR

Ex Output:
DWefw


Ex Input:
fRMacxYHEYXkB, okKNwDacxYHEYXawJPgS

Ex Output:

acxYHEYX