(defvar F0)
(defvar F1)
(defvar N)
(defvar temp)
(setq temp (read-from-string (concatenate 'string "(" (read-line) ")")))

(setq F0 (nth 0 temp))
(setq F1 (nth 1 temp))
(setq N  (nth 2 temp))
;(format t "~d ~d~%" N M)

(setq temp 0)
(format t "~d~%" (case (mod N 3) (0 F0) (1 F1) (otherwise (logxor F0 F1))))