(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)) `(values ,(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
(eval-when (:compile-toplevel :load-toplevel :execute)
  (load-shared-object "libmpfr.so.6" :dont-save t)
  (require :sb-mpfr)
  (add-package-local-nickname :mpfr :sb-mpfr))
(eval-when (:compile-toplevel :load-toplevel :execute)
  (mpfr:set-precision 64))

;;;
;;; Arithmetic operations with static modulus
;;;

;; FIXME: Currently MOD* and MOD+ doesn't apply MOD when the number of
;; parameters is one.
(defmacro define-mod-operations (divisor)
  `(progn
     (defun mod* (&rest args)
       (reduce (lambda (x y) (mod (* x y) ,divisor)) args))

     (defun mod+ (&rest args)
       (reduce (lambda (x y) (mod (+ x y) ,divisor)) args))

     #+sbcl
     (eval-when (:compile-toplevel :load-toplevel :execute)
       (locally (declare (muffle-conditions warning))
         (sb-c:define-source-transform mod* (&rest args)
           (if (null args)
               1
               (reduce (lambda (x y) `(mod (* ,x ,y) ,',divisor)) args)))
         (sb-c:define-source-transform mod+ (&rest args)
           (if (null args)
               0
               (reduce (lambda (x y) `(mod (+ ,x ,y) ,',divisor)) args)))))

     (define-modify-macro incfmod (delta)
       (lambda (x y) (mod (+ x y) ,divisor)))

     (define-modify-macro decfmod (delta)
       (lambda (x y) (mod (- x y) ,divisor)))

     (define-modify-macro mulfmod (multiplier)
       (lambda (x y) (mod (* x y) ,divisor)))))


(declaim (ftype (function * (values fixnum &optional)) read-fixnum))
(defun read-fixnum (&optional (in *standard-input*))
  "NOTE: cannot read -2^62"
  (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 #\-))
                                  (setq 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))))))))

(in-package :cl-user)

(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
;;;

(define-mod-operations +mod+)

(defun solve (as k)
  (declare #.OPT
           (uint31 k)
           ((simple-array int32 (*)) as)
           (inline sort))
  (let* ((n (length as))
         (n+ 0)
         (n- 0)
         (as+ (make-array n :element-type 'uint31 :initial-element 0))
         (as- (make-array n :element-type 'uint31 :initial-element 0)))
    (declare (uint31 n+ n-))
    (dotimes (i n)
      (let ((a (aref as i)))
        (cond ((> a 0)
               (setf (aref as+ n+) a)
               (incf n+))
              ((< a 0)
               (setf (aref as- n-) (- a))
               (incf n-)))))
    (setq as+ (sort as+ #'>)
          as- (sort as- #'>))
    (let ((cumuls+ (make-array (+ n+ 1) :element-type 'uint31 :initial-element 1))
          (cumuls- (make-array (+ n- 1) :element-type 'uint31 :initial-element 1))
          (logcumuls+ (make-array (+ n+ 1)
                                  :element-type 'mpfr:mpfr-float
                                  :initial-element (mpfr:coerce 0d0 'mpfr:mpfr-float)))
          (logcumuls- (make-array (+ n- 1)
                                  :element-type 'mpfr:mpfr-float
                                  :initial-element (mpfr:coerce 0d0 'mpfr:mpfr-float))))
      (dotimes (i n+)
        (let ((a (aref as+ i)))
          (setf (aref cumuls+ (+ i 1))
                (mod* (aref cumuls+ i) a)
                (aref logcumuls+ (+ i 1))
                (mpfr:add (aref logcumuls+ i)
                          (mpfr:log (mpfr:coerce a 'mpfr:mpfr-float))))))
      (dotimes (i n-)
        (let ((a (aref as- i)))
          (setf (aref cumuls- (+ i 1)) (mod* (aref cumuls- i) a)
                (aref logcumuls- (+ i 1))
                (mpfr:add (aref logcumuls- i)
                          (mpfr:log (mpfr:coerce a 'mpfr:mpfr-float))))))
      (let ((res 0)
            (maxlog (mpfr:coerce -1d100 'mpfr:mpfr-float)))
        (loop for d- from 0 to k by 2
              for d+ = (- k d-)
              when (and (<= d- n-) (<= d+ n+))
              do (let ((log (mpfr:add (aref logcumuls+ d+) (aref logcumuls- d-))))
                   (when (mpfr:> log maxlog)
                     (setq maxlog log
                           res (mod* (aref cumuls+ d+) (aref cumuls- d-))))))
        res))))

(defun main ()
  (declare (inline sort))
  (let* ((n (read))
         (k (read))
         (as (make-array n :element-type 'int32 :initial-element 0)))
    (dotimes (i n)
      (setf (aref as i) (read-fixnum)))
    (let ((num+ (count-if #'plusp as))
          (num- (count-if #'minusp as)))
      (println
       (if (loop for d- from 0 to k by 2
                 for d+ = (- k d-)
                 thereis (and (<= d- num-) (<= d+ num+)))
           (solve as k)
           (let ((as (sort as #'< :key #'abs)))
             (reduce #'mod* as :end k :initial-value 1)))))))

#-swank (main)

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

#+swank
(defun io-equal (in-string out-string &key (function #'main) (test #'equal))
  "Passes IN-STRING to *STANDARD-INPUT*, executes FUNCTION, and returns true if
the string output to *STANDARD-OUTPUT* is equal to OUT-STRING."
  (labels ((ensure-last-lf (s)
             (if (eql (uiop:last-char s) #\Linefeed)
                 s
                 (uiop:strcat s uiop:+lf+))))
    (funcall test
             (ensure-last-lf out-string)
             (with-output-to-string (out)
               (let ((*standard-output* out))
                 (with-input-from-string (*standard-input* (ensure-last-lf in-string))
                   (funcall function)))))))

#+swank
(defun get-clipbrd ()
  (with-output-to-string (out)
    #+os-windows (run-program "powershell.exe" '("-Command" "Get-Clipboard") :output out :search t)
    #+os-unix (run-program "xsel" () :output out :search t)))

#+swank (defparameter *this-pathname* (uiop:current-lisp-file-pathname))
#+swank (defparameter *dat-pathname* (uiop:merge-pathnames* "test.dat" *this-pathname*))

#+swank
(defun run (&optional thing (out *standard-output*))
  "THING := null | string | symbol | pathname

null: run #'MAIN using the text on clipboard as input.
string: run #'MAIN using the string as input.
symbol: alias of FIVEAM:RUN!.
pathname: run #'MAIN using the text file as input."
  (let ((*standard-output* out))
    (etypecase thing
      (null
       (with-input-from-string (*standard-input* (delete #\Return (get-clipbrd)))
         (main)))
      (string
       (with-input-from-string (*standard-input* (delete #\Return thing))
         (main)))
      (symbol (5am:run! thing))
      (pathname
       (with-open-file (*standard-input* thing)
         (main))))))

#+swank
(defun gen-dat ()
  (uiop:with-output-file (out *dat-pathname* :if-exists :supersede)
    (format out "200000 100000~%")
    (dotimes (i 200000)
      (println (- (random 1000000000) 500000000) out))))

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

;; To run: (5am:run! :sample)
#+swank
(it.bese.fiveam:test :sample
  (it.bese.fiveam:is
   (common-lisp-user::io-equal "4 2
1 2 -3 -4
"
    "12
"))
  (it.bese.fiveam:is
   (common-lisp-user::io-equal "4 3
-1 -2 -3 -4
"
    "1000000001
"))
  (it.bese.fiveam:is
   (common-lisp-user::io-equal "2 1
-1 1000000000
"
    "1000000000
"))
  (it.bese.fiveam:is
   (common-lisp-user::io-equal "10 10
1000000000 100000000 10000000 1000000 100000 10000 1000 100 10 1
"
    "999983200
")))


Measured memory_bytes: 195572