rearrange paragraph

Hi there,
I have a book like that:
<p id="2">paragraph 1</p>
<p id="5">paragraph 2</p>
<p id="1">paragraph 3</p>
...
I want to edit it back to an id increase order like this:
<p id="1">paragraph 3</p>
<p id="2">paragraph 1</p>
...
<p id="5">paragraph 2</p>
Does anybody know how to do it?
Thanks in advance