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

[Q]: ZRjPgqbLL, uIsmPgqbBB
[A]: Pgqb


[Q]: FiKGCRXutEOzMqP, xdxRXutEsl
[A]: RXutE


[Q]: SavnVw, iJvnHB
[A]:
vn