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

Ex Input:
WFAPUCgVYbmZiFlacUzyv, xQFiekrgPUCgVYbmZUEtl

Ex Output:
PUCgVYbmZ


Ex Input:
libDFDxIgRiglWfxMVRr, yMltDxIgRiglpms

Ex Output:
DxIgRigl


Ex Input:
IWwtBIJaQNPCVDFzZpLoVaBiF, YzUkUNJaQNPCVDFzENGRBH

Ex Output:

JaQNPCVDFz


