fact: Definition sub_sol sigma x := match dec_enc (sigma x) with | inl (exist _ k _) => k | inr _ => 0 end.
imports: List Arith Lia Undecidability.HOU(std.std calculus.calculus) Undecidability.HOU.second_order(diophantine_equations dowek.encoding) Undecidability.HOU.unification.nth_order_unification