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

feYKRk, PrYKMW
YK

STvKOHq, XMGvKOdyM
vKO

wbWnxqwCasPIEMzHjL, qsJnxqwCasPILKlQEzLe

nxqwCasPI