Guess the missing item from this list: β-4, α-9, α-4, β-3, α-7, α-6, α-1, α-2, β-0, α-3, α-5, α-0, β-6, β-5, α-8, β-1.
Directly answer with only one item. Item format should match the list format. Provide no explanation. Answer format: "{item}."