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