"Conclusion" porblems refer to problems which you may think a lot for a "conclusion" but the codding is very easy. For example, 1919A - Wallet Exchange, 1919B - Plus-Minus Split, 1919C - Grouping Increases, 1919D - 01 Tree and so on.

I am very confused about these problems. Almost always, I'm struggling on one of these problems (maybe C or D or even B in a Div.2 contest). I cannot find such "conclusion" quickly. How can I improve?