fact: Definition oends a (l : list a) : Maybe (a + (a * a)).
imports: Coq.Lists.List Equations(Equations) Equations.Type.EqDec Category.Lib Category.Theory.Coq.Functor Category.Theory.Coq.Applicative Category.Theory.Coq.Monad Category.Theory.Coq.Maybe Coq.Lists.List