(define (shori-hantei xs)
  (letrec ((len (string-length xs))
           (inner
            (lambda (m east west)
              (cond
               ((= 3 east) "East")
               ((= 3 west) "West")
               ((<= len m) "NA")
               (else
                (let ((ch (string-ref xs m)))
                  (cond
                   ((char=? ch #\O)
                    (inner (+ 1 m) (+ 1 east) 0))
                   ((char=? ch #\X)
                    (inner (+ 1 m) 0 (+ 1 west)))
                   (else
                    (inner (+ 1 m) east west)))))))))
    (inner 0 0 0)))

(print (shori-hantei (read-line)))