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

LudFxiaqbX, UWMPnFxiaqikiDx
Fxiaq

aIZIsqL, wxSZIsEnO
ZIs

AKwOqqaNZDdwaBMxiT, gPXSqqaNZDdtlEISux

qqaNZDd