proposition: Lemma prev_nat (n : nat) (p : n > 0): ∑ m, S m = n.
proof: Proof. destruct n as [| n]. { contradiction (negnatlthn0 _ p). } exists n; reflexivity. Defined.
imports: UniMath.Foundations.All UniMath.MoreFoundations.All UniMath.Combinatorics.Maybe UniMath.Combinatorics.StandardFiniteSets UniMath.Algebra.Domains_and_Fields UniMath.Algebra.RigsAndRings