proposition: Theorem le_of_succ_le_succ (a b : mynat) : succ a ≤ succ b → a ≤ b.
proof: Proof. intro f. destruct f as [c f]. exists c. rewrite succ_add in f. rewrite succ_eq_succ_iff in f. exact f. Qed.
imports: Unicode.Utf8 Game.Mynat.Definition Game.Mynat.Add Game.Mynat.Mul Game.Mynat.Le Game.World.Addition Game.World.Multiplication Game.World.Proposition Game.World.AdvancedProposition Game.World.AdvancedAddition Game.World.AdvancedMultiplication