Decrease The Values Of Those By One Where The Value Is Higher Than X?

I have an array similar to this:

0 -> 0
1 -> 5
2 -> 9
3 -> 2
4 -> 1
5 -> 6
6 -> 8
7 -> 7
...

There is no clear logic and that does not matter. I need to decrease the values of those by one where the value is higher than x. How would I do this?

For instance, if x = 5, then that array becomes

0 -> 0
1 -> 5
2 -> 8
3 -> 2
4 -> 1
5 -> 5
6 -> 7
7 -> 6
...

All values higher than 5 were decreased by one.