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:
ICizmXnKMpUH, oDrnmXnKgWXX

Ex Output:
mXnK


Ex Input:
aIdXhuhk, syMdXhOw

Ex Output:

dXh