main() {
	a, b := reverse2(1, 2)
	assert a == 2
	assert b == 1

	c, d, e := reverse3(1, 2, 3)
	assert c == 3
	assert d == 2
	assert e == 1

	f, g, h, i := mix4(1, 2, 3, 4)
	assert f == 4 + 1
	assert g == 3 + 2
	assert h == 2 + 3
	assert i == 1 + 4
}

reverse2(a, b) {
	return b, a
}

reverse3(a, b, c) {
	return c, b, a
}

mix4(a, b, c, d) {
	return d + a, c + b, b + c, a + d
}