instruction:
In this task, you are given two strings A, B. Find the longest common substring in the strings A and B.
question:
bmsrkXGb, GcarkXOZF
answer:
rkX


question:
uGDJixAmSiVaFRmfKRM, NsTGxsJixAmSiVageSw
answer:
JixAmSiVa


question:
tlwUnITnJnSIsNlvRwJEeGfvng, vUgnJnSIsNlvRpmNwzk
answer:

nJnSIsNlvR