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

oZNKLmfxecDfkXEGFkRBYk, tReqkiExecDfkXEGtNZpJVRxC
xecDfkXEG

XWKEpwGRkfCFZGOyZQOoypx, lhQkmVqeRkfCFZGOyugPLqs
RkfCFZGOy

uDGbbuuVqUtVqZWlWWXmZYEfTxxwx, hhstVqZWlWWXmubTt

tVqZWlWWXm