main() {
	assert 0 ^ 0 == 0
	assert 0 ^ 1 == 1
	assert 1 ^ 0 == 1
	assert 1 ^ 1 == 0
	assert 1 ^ 2 == 3
	assert 1 ^ 3 == 2
	assert 2 ^ 0 == 2
	assert 2 ^ 1 == 3
	assert 2 ^ 2 == 0
	assert 2 ^ 3 == 1
	assert 3 ^ 0 == 3
	assert 3 ^ 1 == 2
	assert 3 ^ 2 == 1
	assert 3 ^ 3 == 0
}