| n < nused, n < # zbrar, key ∈ (n = 0 ⊃ (nused = 1 ⊃ ri;ri |≤ zbrar[0].key);(n + 1 = nused ⊃ ri |> zbrar[n - 1].key;(ri |> zbrar[n - 1].key) |≤ zbrar[n].key)), nused ≤ # zbrar ⊦ key ∈ ri |
n = 0, n < # zbrar, n < nused, key ∈ (nused = 1 ⊃ ri;ri |≤ zbrar[0].key), nused ≤ # zbrar ⊦ key ∈ ri
n < # zbrar, n < nused, key ∈ (n + 1 = nused ⊃ ri |> zbrar[n - 1].key;(ri |> zbrar[n - 1].key) |≤ zbrar[n].key), nused ≤ # zbrar ⊦ n = 0, key ∈ ri