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

WjyKtxKtEYjP, vuBZJZyKtxKtXRZs
yKtxKt

qQkmYsYN, UhkmYHSy
kmY

oFLvulwi, kKLvuVT

Lvu