Lemma grtoltunel (X : gr) {R : hrel X} (is : isbinophrel R) {x : X} (isg : R (x^-1) 1) : R 1 x. Proof. assert (r := (pr1 is) _ _ x isg). rewrite (grrinvax X x) in r. rewrite (runax X _) in r. apply r. Defined.
Require Import UniMath.MoreFoundations.Subtypes.