proposition: Lemma pow_5_mod_2 (n: nat) : 5 ^ n mod 2 = 1.
proof: Proof. elim: n; first done. move=> n IH. by rewrite Nat.pow_succ_r' mul_mod ?IH. Qed.
imports: ZArith List PeanoNat Lia Relations.Relation_Operators Relations.Operators_Properties Undecidability.MinskyMachines.MM2 Undecidability.CounterMachines.Util.CM1_facts Undecidability.MinskyMachines.Util.MM2_facts ssreflect ssrbool ssrfun