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

;; BEGIN_INSERTED_CONTENTS
(declaim (ftype (function * (values fixnum &optional)) read-fixnum))
(defun read-fixnum (&optional (in *standard-input*))
  (declare #.OPT)
  (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

;; This is actually not trisection but bisection.
(declaim (inline trisect-left))
(defun trisect-left (target start end &key maximum)
  "TARGET := function | (TODO: vector)

Returns the leftmost index at which TARGET takes the minimum. TARGET must
satisfy the following condition: the signs of TARGET[i+1] - TARGET[i] are
monotone, i.e. -, -, ..., -, 0, 0, ..., 0, +, +, ..., + for i = START, START+1,
..., END-1; convexity or unimodality is sufficient. (If MAXIMUM is true, the
signs are reversed.)

Note that this function searches the optimal value in the **closed** interval
[START, END]."
  (declare (fixnum start end))
  (assert (< start end))
  (let ((ng (- start 1))
        (ok end))
    (declare (fixnum ng ok))
    (if maximum
        (loop
          (if (<= (- ok ng) 1)
              (return ok)
              (let ((mid (ash (+ ok ng) -1)))
                (if (<= (funcall target (+ 1 mid))
                        (funcall target mid))
                    (setq ok mid)
                    (setq ng mid)))))
        (loop
          (if (<= (- ok ng) 1)
              (return ok)
              (let ((mid (ash (+ ok ng) -1)))
                (if (>= (funcall target (+ 1 mid))
                        (funcall target mid))
                    (setq ok mid)
                    (setq ng mid))))))))

(defun main ()
  (declare #.OPT)
  (let* ((n (read))
         (as (make-array n :element-type 'uint32))
         (cumuls (make-array (+ n 1) :element-type 'uint62 :initial-element 0))
         (res most-positive-fixnum))
    (declare (uint62 n res))
    (dotimes (i n)
      (setf (aref as i) (read-fixnum)
            (aref cumuls (+ i 1)) (+ (aref cumuls i) (aref as i))))
    (labels ((query (l r)
               (- (aref cumuls r) (aref cumuls l))))
      (declare (inline query))
      (loop for pivot of-type uint32 from 2 to (- n 2)
            do (let* ((qtile1 (trisect-left (lambda (i)
                                              (abs (- (query 0 i)
                                                      (query i pivot))))
                                            0 pivot))
                      (qtile3 (trisect-left (lambda (i)
                                              (abs (- (query pivot i)
                                                      (query i n))))
                                            pivot n))
                      (p (query 0 qtile1))
                      (q (query qtile1 pivot))
                      (r (query pivot qtile3))
                      (s (query qtile3 n)))
                 (setq res (min res (- (max p q r s) (min p q r s)))))))
    (println res)))

#-swank (main)


Measured memory_bytes: 16872