{A A' B B' : Type} `{Contr A} `{Contr A'} (h : A + B <~> A' + B') : B <~> B' := equiv_unfunctor_sum_indecomposable_ll ((equiv_contr_contr +E 1) oE h).
Require Import HoTT.Basics. Require Import Types.Empty Types.Unit Types.Prod Types.Sigma. Require Import Types.Bool.