(defvar state)
(setq state 1 )
;state
;zero  1
;f5 2
;sev 3
;s5

(defvar ans)
(setq ans "NG~%")
(loop for char = (read-char nil nil) do
    (if (eq char nil) (return))
    (if (not (eq char #\Newline)) (progn
        (values)
    ))
    (case state
        (1
            ;(print "zero")
            (if (eql char #\5) (setq state 2))
        )
        (2   ;(print "f5")
            (if (eql char #\7) (setq state 'sev) (setq state 3))
        )
        (3  ;(print "sev")
            (if (eql char #\5) (progn (setq ans "OK~%") (return)) (setq state 1))
        )
    )
)
(format 't ans)