endings ый / ий of adjectives

[smart888]

Привет!

I have a question about the endings of adjectives. I know that in Russian there are 4 main spelling rules and according to one of them you can't write ы after к, г, х, ж, ш, ч, щ That's why you have to say русский and not русскый etc. But what about words like последний, why do they finish with ий? The letter н doesn't belong to those exceptional letters.

Спасибо за помочь!