(define (solve n s)
  (let loop ([l '()]
             [i 0]
             [c #\x])
    (cond [(= i n) (reverse l)]
          [(and (char=? #\x c)
                (char=? #\o (string-ref s i))) (loop (cons (+ i 1) l) (+ i 1) (string-ref s i))]
          [else (loop l (+ i 1) (string-ref s i))])))

(define (main args)
  (let* ([n (read)]
         [s (symbol->string (read))])
    (let1 l (solve n s)
          (print (length l))
          (if (not (null? l)) (print (string-join (map number->string l) " ")))))
  0)