EDB — 06F

[06F]Build an order \(⪯\) on \(ℕ\) with this property: for each \(n∈ℕ\)

• the set \(\{ k∈ℕ , k≠ n,k⪯ n\} \) of the elements preceding \(n\) has exactly two maximals,

• the set \(\{ k∈ℕ , k≠ n,n⪯ k\} \) of the elements following \(n\) has exactly two minimals.