Thank you for your answer !
Not I'm not really sure... I forget to precise that I try your hack with my old account, with new account all works very well.
And I also have to precise that I have already a large amount of coin. So I can't win coin anymore. I can only use them. So I try to use them and tap N=O+D with D negative. For example I use 50 coins and I tap the difference "-50". I don't know if it's work like that.
In an other forum you give us a technic : spend coins, search N=O+D with D equal of the amount which was spended, and this is give us the total amount of coins used in the game. Then tap -50 hex and normaly this is give us the adress of gems... But this is not works for me... ?