As the saying goes, who makes perfection? If you do more, you will feel better and make fewer mistakes.
Remember not to do mental arithmetic, the heart is a taboo.
Method 2: Ask God.
With luck, everything goes well and everything is ok.
Method 3: Eat well, drink well and sleep well.
Avoid thinking, if thinking can't be buried in numbers all day, you can't master the sense of numbers well and improve the accuracy of operation.