(define (solve ls)
  (cond [(and (>= (length ls) 2)
              (char=? (car ls) #\1)
              (every (cut char=? <> #\3) (cdr ls))) (length (cdr ls))]
        [else -1]))

(define (main args)
  (let ([ls (string->list (read-line))])
    (print (solve ls)))
  0)