[texhax] Reverse page numbering (begin with the last page number and end with 0)

[Othmane Benkirane]

Hello,

The subject explains everything: I want to start the page numbering from the last page number and decrement it until it's 0 (for the last page). A mathematical operation for this would be: \thepage - \pageref{LastPage}, but how to include it in fancyhdr (for a book class) ?

Happy new year,
Othmane Benkirane.