proposition: Lemma minussn1' ( n : nat ) : ( S n ) - 1 = n.
proof: Proof. destruct n; apply idpath. Defined.
imports: UniMath.Foundations.All UniMath.MoreFoundations.All UniMath.Combinatorics.Maybe UniMath.Combinatorics.StandardFiniteSets UniMath.Algebra.Domains_and_Fields UniMath.Algebra.RigsAndRings