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

Ex Input:
jFVaEHbMrrkW, ekfVaEHbPnBnM

Ex Output:
VaEHb

Ex Input:
IzwlZDJSEFPxfIud, xwWSYwlZDJSEFPbvSXTlS

Ex Output:
wlZDJSEFP

Ex Input:
wCfNCfxvLRAxBstRTwMSqTn, AhwxfFNCfxvLRAxBrNtf

Ex Output:
NCfxvLRAxB