(LETREC FIRST
  (FIRST LAMBDA (X)
    (IF (EQ X (QUOTE NIL)) (QUOTE NIL)
        (IF (EQ (CAR X) (QUOTE NIL)) (QUOTE NIL)
            (IF (ATOM X) (QUOTE NIL)
                (CONS (CAR (CAR X)) (FIRST (CDR X))))))))&