import Data.Bits

zipWith' :: (a -> b -> c) -> [a] -> [b] -> [c]
zipWith' f (x:xs) (y:ys) = let z = f x y in z `seq` z : zipWith' f xs ys
zipWith' _ _ _ = []

fib :: Int -> Int -> [Int]
fib a b = a : b : zipWith' xor xs (tail xs) where
    xs = fib a b

main = do
        [a, b, n] <- fmap (map read . words) getLine
        print $ fib a b !! (n `mod` 3)