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

SUgXyznbUQRpiLUTlRb, jlnwLTnbUQRpioUFyJ
nbUQRpi

WjyKtxKtEYjP, vuBZJZyKtxKtXRZs
yKtxKt

ykgTBKNEJ, wfgTBKiOq

gTBK