;; -*- coding: utf-8 -*-
(eval-when (:compile-toplevel :load-toplevel :execute)
  (sb-int:defconstant-eqx OPT
    #+swank '(optimize (speed 3) (safety 2))
    #-swank '(optimize (speed 3) (safety 0) (debug 0))
    #'equal)
  #+swank (ql:quickload '(:cl-debug-print :fiveam) :silent t)
  #-swank (set-dispatch-macro-character
           #\# #\> (lambda (s c p) (declare (ignore c p)) (read s nil nil t))))
#+swank (cl-syntax:use-syntax cl-debug-print:debug-print-syntax)
#-swank (disable-debugger) ; for CS Academy

;; BEGIN_INSERTED_CONTENTS
;; Should we do this with UNWIND-PROTECT?
(defmacro with-buffered-stdout (&body body)
  "Buffers all outputs to *STANDARD-OUTPUT* in BODY and flushes them to
*STANDARD-OUTPUT* after BODY has been done (without error). Note that only
BASE-CHAR is allowed."
  (let ((out (gensym)))
    `(let ((,out (make-string-output-stream :element-type 'base-char)))
       (let ((*standard-output* ,out))
         ,@body)
       (write-string (get-output-stream-string ,out)))))

(declaim (ftype (function * (values fixnum &optional)) read-fixnum))
(defun read-fixnum (&optional (in *standard-input*))
  (macrolet ((%read-byte ()
               `(the (unsigned-byte 8)
                     #+swank (char-code (read-char in nil #\Nul))
                     #-swank (sb-impl::ansi-stream-read-byte in nil #.(char-code #\Nul) nil))))
    (let* ((minus nil)
           (result (loop (let ((byte (%read-byte)))
                           (cond ((<= 48 byte 57)
                                  (return (- byte 48)))
                                 ((zerop byte) ; #\Nul
                                  (error "Read EOF or #\Nul."))
                                 ((= byte #.(char-code #\-))
                                  (setf minus t)))))))
      (declare ((integer 0 #.most-positive-fixnum) result))
      (loop
        (let* ((byte (%read-byte)))
          (if (<= 48 byte 57)
              (setq result (+ (- byte 48)
                              (* 10 (the (integer 0 #.(floor most-positive-fixnum 10)) result))))
              (return (if minus (- result) result))))))))

(defmacro dbg (&rest forms)
  #+swank
  (if (= (length forms) 1)
      `(format *error-output* "~A => ~A~%" ',(car forms) ,(car forms))
      `(format *error-output* "~A => ~A~%" ',forms `(,,@forms)))
  #-swank (declare (ignore forms)))

(defmacro define-int-types (&rest bits)
  `(progn
     ,@(mapcar (lambda (b) `(deftype ,(intern (format nil "UINT~A" b)) () '(unsigned-byte ,b))) bits)
     ,@(mapcar (lambda (b) `(deftype ,(intern (format nil "INT~A" b)) () '(signed-byte ,b))) bits)))
(define-int-types 2 4 7 8 15 16 31 32 62 63 64)

(declaim (inline println))
(defun println (obj &optional (stream *standard-output*))
  (let ((*read-default-float-format* 'double-float))
    (prog1 (princ obj stream) (terpri stream))))

(defconstant +mod+ 1000000007)

;;;
;;; Body
;;;

(declaim (inline zeta-subtransform!))
(defun zeta-subtransform! (vector &optional (plus #'+))
  (declare (vector vector))
  (let* ((n (length vector))
         ;; cardinality of the underlying set
         (card (- (integer-length n) 1)))
    (assert (= 1 (logcount n)))
    (dotimes (i card)
      (let ((mask (ash 1 i)))
        (dotimes (j n)
          (unless (zerop (logand j mask))
            (setf (aref vector j)
                  (funcall plus
                           (aref vector j)
                           (aref vector (logxor j mask))))))))
    vector))

(declaim (inline moebius-subtransform!))
(defun moebius-subtransform! (vector &optional (minus #'-))
  (declare (vector vector))
  (let* ((n (length vector))
         (card (- (integer-length n) 1)))
    (assert (= 1 (logcount n)))
    (dotimes (i card)
      (let ((mask (ash 1 i)))
        (dotimes (j n)
          (unless (zerop (logand j mask))
            (setf (aref vector j)
                  (funcall minus
                           (aref vector j)
                           (aref vector (logxor j mask))))))))
    vector))

;; originally written by g000001 (See https://g000001.cddddr.org/1248011028)
(declaim (inline (setf nthcdr*)))
(defun (setf nthcdr*) (subst pos lst)
  (case pos
    (0 (if (null subst)
           lst
           (progn (rplaca lst (car subst))
                  (rplacd lst (cdr subst)))))
    (1 (rplacd lst subst))
    (otherwise
     (let ((suffix (nthcdr (1- pos) lst)))
       (when suffix
         (rplacd suffix subst))))))

(declaim (inline prefix!))
(defun prefix! (list end)
  (setf (nthcdr* end list) nil)
  list)

;; 添え字集合∪添え字集合で大きいほう2つを残すという操作を⊕とすると、結合的かつ可換。
;; つまり、F(S) = ⊕_{T ⊆ S} f(T)を求めれば良いけど、fは何？
;; → f(T) = {T}か。
;; これでi∨j ⊆ K に対する最大値は求まる。
;; i∨j <= K ⇔ k∈[K]が存在してi∨j = k
;; ⇒ k∈[K]が存在してi∨j⊆k
;; 最後は逆も成り立つ。k∈[K]が与えられたとき、任意のl⊆kについてl∈Kだから

(defun main ()
  (declare (inline sort nunion)
           #.OPT)
  (let* ((n (read))
         (power (expt 2 n))
         (as (make-array power :element-type 'uint32))
         (dp (make-array power :element-type 'list)))
    (declare ((integer 1 18) n))
    (dotimes (i power)
      (setf (aref as i) (read-fixnum)
            (aref dp i) (list i)))
    (zeta-subtransform!
     dp
     (lambda (set1 set2)
       (prefix! (sort (nunion (copy-list set1)
                              (copy-list set2))
                      #'>
                      :key (lambda (i) (aref as i)))
                2)))
    (let ((res 0))
      (declare (uint32 res))
      (with-buffered-stdout
        (loop for x from 1 below power
              for (idx1 idx2) = (aref dp x)
              do (setf res (max res (+ (aref as idx1) (aref as idx2))))
                 (println res))))))

#-swank (main)


Measured memory_bytes: 89700