I want to show prefix notation in my document, somewhat like this:

```
+ (x 5 3) (- 6 4)

```

However, I want to enter it in maths mode, but maths mode removes all the spaces, so I get

```
+(x53)(-64)

```

Which has rather a different meaning. Obviously I could add spaces explicitly, but

```
$+\;(\times\;5\;3)\;(-\;6\;4) $

```

is not exactly readable in the source.

Any better ways of doing this?