import Data.Bits

fact :: [Integer] -> Integer
fact [f0, f1, n]
    | n == 0    = f0
    | n == 1    = f1
    | otherwise = f f1 f0 (n - 2)
    where
    f a b i | i == 0    = a `xor` b
            | otherwise = f (a `xor` b) a (i - 1)

main = getLine >>= print . fact . map read . words