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

QeNePjbLBKbDOuAVTJtXL, xjPVOyPbLBKbDOuDsMSEF
bLBKbDOu

QECPAHsg, bUfPAHOWb
PAH

AGRVsdfOv, dHHwRVsdKS

RVsd