# Solution

```rust,editable
{{#include exercise.rs:solution}}
```

<details>

- Note that the argument `n` is marked as `mut`, allowing you to change the
  value of `n` in the function. Like variables, function arguments are immutable
  by default and you must add `mut` if you want to modify their value. This does
  not affect how the function is called or how the argument is passed in.

</details>
