(defun main (&rest argv)
  (declare (ignorable argv))
  (let* ((s (read-line))
         (n (length s)))
    (format t "~d~%" (if (and (>= n 2)
                              (char= #\1 (char s 0))
                              (not (find #\3 s :test (complement #'char=) :start 1)))
                         (1- n)
                         -1))))

(main)