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

Q: vytthSjj, XVttthSFAvk

A: tthS
****
Q: vSFxjd, AHFxpi

A: Fx
****
Q: XMDcTnDOwTxfVYFKP, usSZqjPrscTnDOwTxfVZKYslsvu

A:
cTnDOwTxfV
****