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

ztkWLUJQXxP, fYluOkWLUJKDX
kWLUJ

spGRUmIYuGl, qkqRUmItqU
RUmI

UaqYGWcUHYzyY, ZGrnPqYGWcUHMtwiM

qYGWcUH