Which function provide this output?

Hello everyone!

I need a function f(x), where x are positive integers, that provides the following output pattern:

x: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18...

f(x): 7 6 5 4 3 2 1 0 7 6 5 4 3 2 1 0 7 6...

Thanks in advance!

[Walter Roberson]

Hint:

remainder when 1 is divided by 8 is 1, target value is 7, sum of remainder and target value is ...

remainder when 2 is divided by 8 is 2, target value is 6, sum of remainder and target value is ...

[Basil C.]

I think you mean difference of remainder and target value @Walter Roberson

[Walter Roberson]

No, I mean sum. 1 remainder, desired value is 7, sum is 8