(defun main (&rest argv)
  (declare (ignorable argv))
  (let* ((*read-default-float-format* 'double-float)
         (n (read))
         (d (read))
         (s (read))
         (x (make-array n :element-type 'integer :initial-element 0))
         (res (* n (1+ (* 2 s)))))
    (dotimes (i n) (setf (aref x i) (read)))
    (sort x #'<)
    (dotimes (i n)
      (loop for j from (1+ i) below n do
            (let ((dst (abs (- (aref x i) (aref x j)))))
                (when (zerop (mod dst d))
                      (let ((tmp (1+ (- (* 2 s) (floor dst d)))))
                        (when (plusp tmp)
                              (decf res tmp)
                              (return)))))))
    (format t "~d~%" res)))

(main)