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

vhZuXCsIkQR, YflCuXCsIkLu
uXCsIk

kOrQWjLKnwN, xFsWjLKgr
WjLK

XZiCysFwMTHvwvMEAizD, ClHBDiEysFwMTHvJHGUMRoD

ysFwMTHv