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

xQcYRVFFqrVAMsBm, VErcKZvcYRVFFqzKo
cYRVFFq

rPPfxUdowLLdvwRtY, PuHovApkfxUdowLLBOhq
fxUdowLL

JeUeoxQbHcAsZNFfnvM, bjrvMlDtKoxQbHcAsZNTAQ

oxQbHcAsZN