K
ϕ < 0
ϕ ∈ [ 0, α ]
ϕ > α
condition
− ϕ α
0
ϕ α − 1
ϕ α is an integer
⌊ − ϕ α ⌋ + 1
⌊ ϕ α ⌋
ϕ α is not an integer