import qualified Data.Bits as B

main = do
    [f0, f1, n] <- map read . words <$> getLine
    putStrLn . show $ solve f0 f1 n

solve :: Integer -> Integer -> Integer -> Integer
solve f0 f1 n =
    case n `mod` 3 of
         0 -> f0
         1 -> f1
         2 -> f0 `B.xor` f1