instruction:
In this task, you are given two strings A, B. Find the longest common substring in the strings A and B.
question:
libDFDxIgRiglWfxMVRr, yMltDxIgRiglpms
answer:
DxIgRigl


question:
fVEFJa, WtEFYK
answer:
EF


question:
fUNLFrYHev, tAuONLFrYIVZFq
answer:

NLFrY