local ffi = require 'ffi'
local C = ffi.C

ffi.cdef [[
long atol(const char *str);
int printf(const char *fmt, ...);
]]

function split(s, p, f)
	local t = {}
	for e in s:gmatch(p) do
		table.insert(t, f(e))
	end

	return unpack(t)
end

local zero, one = ffi.new("long", 0), ffi.new("long", 1)
local two, three = one + one, one + one + one

function ltob(n)
	if n == zero then return "0" end

	local s = ""
	while n > zero do
		s = s .. (n%two ~= zero and "1" or "0")
		n = n / two
	end
	return s
end

function lxor(n1, n2)
	local s1, s2 = ltob(n1), ltob(n2)
	local n3, i, p = ffi.new("long", 0), 1, ffi.new("long", 1)

	while true do
		local c1, c2 = s1:sub(i,i), s2:sub(i,i)
		if c1 == "" or c2 == "" then break end
		n3 = n3 + p * (c1 ~= c2 and one or zero)
		i, p = i + 1, p * two
	end

	(#s1 > #s2 and s1 or #s1 < #s2 and s2 or ""):sub(i):gsub(".", function (e)
		n3 = n3 + p * (e == "1" and one or zero)
		p = p * two
	end)

	return n3
end

local f0, f1, n = split(io.stdin:read("*l"), "%d+", C.atol)
local f2 = lxor(f0, f1)

C.printf("%ld\n", n % three == zero and f0 or n % three == one and f1 or f2)