(defun colorcheck (i c) (if (zerop (mod i 2)) (if (equal c #\B) #\W #\B) c))

(defun ichimatsu (w c) (if (= w 1) (cons c nil) (cons (colorcheck w c) (ichimatsu (- w 1) c))))

(defun main () (let ((W (read)) (H (read)) (C (read-char)))
    (dotimes (i H) (format t "~A~%" (coerce (reverse (ichimatsu W (colorcheck (+ i 1) C))) 'string)))))

(main)