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

yQCDWefwvrPP, RwoMDWefwhSxTR
DWefw

uRLpAWCotLmxcSmKyvo, laotLmxcSmKyBwVfJB
otLmxcSmKy

WuKpvvsQgdIWYoDfz, bWWFKpvvsQgdknPGoi

KpvvsQgd