C.printf((function (f, s)
	return f(s)
end)(function (s)
	local s0,s1,n = s:match("(%d+)%s(%d+)%s(%d+)")
	local f0,f1,r = C.atol(s0),C.atol(s1),C.atol(n)%3LL
	local f2,p = 0LL,1LL
	while f0 ~= 0LL and f1 ~= 0LL do
		f0,f1,f2,p = f0/2LL,f1/2LL,f2+p*(f0%2LL ~= f1%2LL and 1LL or 0LL),p*2LL
	end
	if f0 ~= 0LL then while f0 ~= 0LL do f0,f2,p = f0/2LL,f2+p*(f0%2LL),p*2LL end end
	if f1 ~= 0LL then while f1 ~= 0LL do f1,f2,p = f1/2LL,f2+p*(f1%2LL),p*2LL end end

	if r == 0LL then
		return "%s\n", s0
	elseif r == 1LL then
		return "%s\n", s1
	else
		return "%ld\n", f2
	end
end, io.stdin:read("*l")))