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

WFAPUCgVYbmZiFlacUzyv, xQFiekrgPUCgVYbmZUEtl
PUCgVYbmZ

IJQqdzqdaGEIcdyh, izlVdzqdaGGiPYz
dzqdaG

ixHaFYJXkRJLYh, QnerYJXkReEIqP

YJXkR