; 文字列の中から OOO と XXX 文字列を検索し比較する
(defun main (&rest argv)
  (declare (ignorable argv))
  (let* ((s (read-line))
                     ; search sequence-1 sequence-2 &key from-end test test-not key start1 start2 end1 end2 ⇒ position
                     ; sequence-2 の中で sequence-1 のある位置を返す
                     ; (search "OOO" "OXXOXOXXOOO") => 8
                     ; (search "OOO" "OXXOXOXXXOO") => nil
         (east-check (search "OOO" s))
         (west-check (search "XXX" s)))
    (princ (cond
            ((and (null east-check) (null west-check)) 'NA)
            ((null east-check) (if (< west-check 3) 'NA "West"))
            ((null west-check) (if (< east-check 3) 'NA "East"))
            (t (if (< east-check west-check) "East" "West"))))
    (terpri)))
(main)