(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))

(defun main ()
  (let* ((n (read))
         (as (read-into n 'vector))
         (movable (make-array n :initial-element nil))
         (next (make-array n :initial-element (1- n))))
    (dotimes (i (1- n))
      (when (and (plusp i)
                 (= 1 (logxor (aref as i)
                              (aref as (1- i)))))
        (setf (aref movable i) t)))
    (loop :for i :from (- n 2) :downto 0
          :do (setf (aref next i)
                    (if (aref movable i)
                        (aref next (1+ i))
                        i)))
    (let ((res 0))
      (dotimes (i (1- n))
        (when (= 1 (aref as i))
          (let ((dist (aref next (1+ i))))
            (incf res (- dist i)))))
      (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)))