import qualified Data.Text as T
import Control.Applicative
import Data.Bits
main = do
	inputs<-fmap (read.T.unpack)<$>T.split (==' ')<$>T.pack<$>getLine::IO [Integer]
	let f0=inputs!!0
	let f1=inputs!!1
	let n =inputs!!2
	let n_m=n `mod` 3
	print$if n_m==0 then f0 else if n_m==1 then f1 else f0 `xor` f1