Difficult exercises suitable for top students. According to the content of Meng Guang's Thesis, the topic of Duan is very difficult, which is suitable for top students who are good at mathematics to achieve stable results. Solving a large number of final exam questions can help students expand their way of thinking and solve problems. Duan, a native of Suqian, Jiangsu Province, won the second prize in the basic skills competition for young junior high school mathematics teachers in Jiangsu Province and the first prize in the junior high school mathematics proposition competition in Yangzhou City. Many papers were published in magazines above the provincial level.