(in-package :cl-user)
(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 :cp/util) :silent t)
  #+swank (use-package :cp/util :cl-user)
  #-swank (set-dispatch-macro-character
           #\# #\> (lambda (s c p) (declare (ignore c p)) `(values ,(read s nil nil t)))))
#+swank (set-dispatch-macro-character #\# #\> #'cl-debug-print:debug-print-reader)

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

(defconstant +mod+ 1000000007)

(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)))

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

;; BEGIN_INSERTED_CONTENTS
(defpackage :cp/modify-macro
  (:use :cl)
  (:export #:minf #:maxf #:mulf #:divf #:iorf #:xorf #:andf))
(in-package :cp/modify-macro)

(macrolet ((def (name fname)
             `(define-modify-macro ,name (new-value) ,fname)))
  (def minf min)
  (def maxf max)
  (def mulf *)
  (def divf /)
  (def iorf logior)
  (def xorf logxor)
  (def andf logand))

;; BEGIN_USE_PACKAGE
(eval-when (:compile-toplevel :load-toplevel :execute)
  (use-package :cp/modify-macro :cl-user))
(in-package :cl-user)

;;;
;;; Body
;;;

(defun main ()
  (declare #.*opt*)
  (let* ((n (read))
         (k (read))
         (nums (coerce (loop repeat n collect (float (read) 1f0))
                       '(simple-array single-float (*))))
         (state (make-array n :element-type 'uint8 :initial-element 0))
         (sums (make-array k :element-type 'single-float :initial-element 0f0))
         (counts (make-array k :element-type 'uint8 :initial-element 0))
         (achievement 1)
         (res 0))
    (declare (uint4 n k achievement))
    (setf (aref sums 0) (aref nums 0)
          (aref counts 0) 1)
    (labels ((inc-count (i)
               (incf (aref counts i))
               (when (= 1 (aref counts i))
                 (incf achievement)))
             (dec-count (i)
               (decf (aref counts i))
               (when (= 0 (aref counts i))
                 (decf achievement)))
             (update! ()
               (unless (find 0 counts)
                 (loop for sum across sums
                       for count across counts
                       maximize (/ sum count) into max
                       minimize (/ sum count) into min
                       do (maxf res (ceiling (- max min 1f-6))))))
             (dfs (pos)
               (when (>= (+ achievement (- n pos)) k)
                 (if (= pos n)
                     (update!)
                     (dotimes (i k)
                       (setf (aref state pos) i)
                       (incf (aref sums i) (aref nums pos))
                       (inc-count i)
                       (dfs (+ pos 1))
                       (decf (aref sums i) (aref nums pos))
                       (dec-count i))))))
      (dfs 1)
      (println res))))

#-swank (main)

;;;
;;; Test and benchmark
;;;

#+swank
(progn
  (defparameter *lisp-file-pathname* (uiop:current-lisp-file-pathname))
  (setq *default-pathname-defaults* (uiop:pathname-directory-pathname *lisp-file-pathname*))
  (defparameter *dat-pathname* (uiop:merge-pathnames* "test.dat" *lisp-file-pathname*))
  (defparameter *problem-url* "https://yukicoder.me/problems/no/21"))

#+swank
(defun gen-dat ()
  (uiop:with-output-file (out *dat-pathname* :if-exists :supersede)
    (format out "9 9~%")
    (dotimes (_ 9)
      (println (+ 1 (random 1000)) out))))

#+swank
(defun bench (&optional (out (make-broadcast-stream)))
  (time (run *dat-pathname* out)))

#-swank
(eval-when (:compile-toplevel)
  (when (or (> sb-c::*compiler-warning-count* 0)
            sb-c::*undefined-warnings*)
    (error "count: ~D, undefined warnings: ~A"
           sb-c::*compiler-warning-count*
           sb-c::*undefined-warnings*)))

;; To run: (5am:run! :sample)
#+swank
(5am:test :sample
  (5am:is
   (equal "535
"
          (run "5
3
555
20
432
301
21
" nil)))
  (5am:is
   (equal "651
"
          (run "8
4
329
980
656
738
739
542
873
501
" nil))))