I am trying to use afconvert to convert a .mp3 to .m4r. I am entering the following:

```
afconvert -f m4af -d aac -o input.mp3 tone.m4r

```

However, this gives me an error:

```
Error: Couldn't open input file (-43)

```

I am in the directory of the input file. Could someone please shed some light on what I am doing wrong?