(defun main (&rest argv)
  (declare (ignorable argv))
  (let* ((s (read-line))
         (dp (make-array (list 2 21 21 21 21) :element-type 'integer :initial-element -1))
         (a 0)
         (b 1)
         (res 0))
    (setf (aref dp 0 0 0 0 0) 0)
    (loop for c across s do
          (dotimes (k 21)
            (dotimes (u (1+ k))
              (dotimes (r (1+ u))
                (dotimes (o (1+ r))
                  (let ((now (aref dp a k u r o)))
                    (unless (= now -1)
                            (setf (aref dp b k u r o) (max (aref dp b k u r o) now))
                            (when (and (or (char= c #\K) (char= c #\?)) (<= (1+ k) 20))
                                  (setf (aref dp b (1+ k) u r o) (max (aref dp b (1+ k) u r o) now)))
                            (when (and (or (char= c #\U) (char= c #\?)) (<= (1+ u) k))
                                  (setf (aref dp b k (1+ u) r o) (max (aref dp b k (1+ u) r o) now)))
                            (when (and (or (char= c #\R) (char= c #\?)) (<= (1+ r) k))
                                  (setf (aref dp b k u (1+ r) o) (max (aref dp b k u (1+ r) o) now)))
                            (when (and (or (char= c #\O) (char= c #\?)) (<= (1+ o) k))
                                  (setf (aref dp b k u r (1+ o)) (max (aref dp b k u r (1+ o)) now)))
                            (when (and (or (char= c #\I) (char= c #\?)) (<= (1+ now) o))
                                  (setf (aref dp b k u r o) (max (aref dp b k u r o) (1+ now))))))))))
          (rotatef a b))
    (dotimes (k 21)
      (dotimes (u (1+ k))
        (dotimes (r (1+ u))
          (dotimes (o (1+ r))
            (setq res (max res (aref dp a k u r o)))))))
    (format t "~d~%" res)))

(main)