proposition: Theorem succ_inj' {a b : mynat} (hs : succ(a) = succ(b)) : a = b.
proof: Proof. apply succ_inj. exact hs. Qed.
imports: Unicode.Utf8 Game.Mynat.Definition Game.Mynat.Add Game.World.Addition Game.World.Proposition Game.World.AdvancedProposition Setoid