Fair and square
Fair is often in the eye of the beholder. What you think is fair might depend on where you are in the transaction. Losers tend to think an outcome is more unfair than winners do.
But square?
The thing about square is that everyone can agree on that part.
If something is fair and square, then the losers can concur with the winners, because square isn’t relative.
The secret is simple: if the calculations look the same regardless of what you’re rooting for, then you’ve found the method. The outcome should be unrelated to the method.