(in-package #:cl-user)

;;------------------------------Preferences------------------------------

(eval-when (:compile-toplevel :load-toplevel :execute)
  #+swank (declaim (optimize (speed 3) (safety 2)))
  #-swank (declaim (optimize (speed 3) (safety 0) (debug 0)))
  #+swank (load "~/ghq/github.com/motoshira/atcoder-submission/ac-tools/act.lisp")
  #+swank (ql:quickload :prove)
  #-swank (declaim (sb-ext:muffle-conditions sb-ext:compiler-note))
  #-swank (sb-ext:disable-debugger)
  (pushnew :inline-generic-funcion *features*))

;;---------------------------------Body---------------------------------

(in-package #:cl-user)

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

(defun read-into (count &optional (result-type 'list) (reader #'read))
  (coerce (loop :repeat count :collect (funcall reader)) result-type))

(defconstant +inf+ #.(ash 1 60))

(defun main ()
  (let* ((n (read))
         (m (read))
         (as (read-into n))
         (bs (read-into m))
         (es nil))
    ;; blue -> 0
    ;; red  -> 1
    (dolist (a as)
      (push (list a 1) es))
    (push (list +inf+ 1) es)
    (push (list (- +inf+) 1) es)
    (dolist (b bs)
      (push (list b 0) es))
    (setf es (sort es #'< :key #'first))
    (let ((res 0)
          (cs nil)
          (a nil))
      (flet ((push-blue! (blue)
               (push blue cs))
             (inc-and-flush-blue! (red)
               (declare (fixnum red))
               (when a
                 (incf res
                       (- (1- (abs (- red a)))
                          (loop :for (b0 b1) :on (concatenate 'list
                                                              (list a)
                                                              (reverse cs)
                                                              (list red))
                                :by #'cdr
                                :when b1
                                  :maximize (1- (- b1 b0))))))
               (setf a red
                     cs nil)))
        (loop :for (value type) :in es
              :do (ecase type
                    (0 (push-blue! value))
                    (1 (inc-and-flush-blue! value))))
        (println res)))))

#-swank (main)

#+swank
(defun run ()
  (let ((*standard-input*
          (make-string-input-stream
           (with-output-to-string (*standard-output*)
             (run-program
              (merge-pathnames "copy-or-paste" (truename "~/bin/"))
              '()
              :output *standard-output*)))))
    (main)))