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

[EX Q]: mvIvSzMtYsfVLdaGEmef, wnzMtYsfVLdaKm
[EX A]: zMtYsfVLda

[EX Q]: STvKOHq, XMGvKOdyM
[EX A]: vKO

[EX Q]: kzJNrpjnSKFKuIIUE, grqskCzpjnSKFKDgVHH
[EX A]:
pjnSKFK