proposition: Theorem R_markov : ~ (forall n, P n) -> exists n, ~ P n.
proof: Proof. intros Hneg. destruct (l_not_R0 f) as [N HN]. intros Hf. apply Hneg. intros n; apply l_R0 with (n := n) in Hf. apply Heq2; assumption. exists N; apply Heq1; assumption. Qed.
imports: Reals Lia Lra