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

[EX Q]: gwVLygvd, VOQLyglfo
[EX A]: Lyg

[EX Q]: cvZfWOwa, xOfWOhZs
[EX A]: fWO

[EX Q]: RkndwURjXHNEGwDmdn, QduURjXHNEGZlUIZA
[EX A]:
URjXHNEG