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