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

yJRITYgVTSNsPjG, NSIdKYgVTSNmj
YgVTSN

IzwlZDJSEFPxfIud, xwWSYwlZDJSEFPbvSXTlS
wlZDJSEFP

roCFKWBMhlUElO, LTfKSCFKWBMVht

CFKWBM