The topic is not very clear, so I don't know the structure of the last part of 4 ~ but all the score calculation should be separated step by step ~ that is, the complex score calculation can be divided into several small pieces. For example, this inversion problem can be divided into the front part and the back part according to the multiplication sign ~ then attack one by one, and finally multiply ~ For each part, adopt the same division and recalculation method, and don't skip it at first ~ Pay attention to whether there are any reducible parts or simplified formulas in the intermediate calculation.