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

cvZfWOwa, xOfWOhZs
fWO

iMwanJBuMdiZDL, kIafHeBuMdiZmKNA
BuMdiZ

xVgYMNSCTpi, UZeWYMNSrh

YMNS