def Try[A](a: => A): Either[Exception, A] =
    try Right(a)
    catch { case e: Exception => Left(e) }

  def sequence[E, A](es: List[Either[E, A]]): Either[E, List[A]] = {
//    Try(es.map(
//      x => x match {
//        case Left(value) => throw new RuntimeException()
//        case Right(value) => value
//      }
//    ))
    es match {
      case Right(value) :: Nil => Right(List(value))
      case Left(value) :: tail => Left(value)
      case Right(value) :: tail => tail.foldLeft(
        x => x match {
          case Right(value) => x ::
        },
        Nil
      )
    }
  }