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

wCfNCfxvLRAxBstRTwMSqTn, AhwxfFNCfxvLRAxBrNtf
NCfxvLRAxB

rCFrfkmXbSHK, mztfkmXwez
fkmX

nDQdZALrLfgO, uAbZALrCUW

ZALr