efficient = ??? i = 0 i = ie e h ( n / 2 + d - i ) ??? e h ( n / 2 + 1 + d + i ) / EL h / ER h Mathematical Formula 5 The ???given number??? referred to in the present embodiment differs according to the processing capability of the hardware used for the processing such as a computer system, required detection accuracy, detection time, and so on in the same way as in the above-described embodiment