A first circuit outputs a third signal having a first level during a period over which first and second signals have the same level, and having a second level during a period over which the first and second signals have different levels. A second circuit outputs a fifth signal having the first level during a period over which a fourth signal having the same level as the third signal has the same level as the first signal, and having the second level during a period over which the first and fourth signals have different levels. A third circuit outputs a sixth signal having a third level during a period over which the second and fifth signals have the same level, and having a fourth level during a period over which the second and fifth signals have different levels.