Every problem is difficult to solve. In recent years, the national volume is the derivative finale, followed by conic curve, and the series is generally simple, but that's how they solve the problem. For Beijing, Jiangsu and other math volumes, we mainly focus on thinking innovation, and the finale is full of uncertainty. It's hard to give you the finale of the series. The difficulty here is that it is difficult to remember, but it may be simple to calculate. Even the Beijing volume has a finale that integrates basic concepts, which is particularly difficult.