Dynamic numbering of lists in xslt

I am a newbie to xslt and XSLFO. I have to do a numbering which offers the
flexibility to reorder elements if an element in between is being removed.

<chapter1>
  <section>first section<section>
</chapter1>
<chapter1>
 <section>second section</section>
</chapter1>
<chapter1>
 <section>third section</section>
</chapter1>
<chapter1>
 <section>fourth section</section>
</chapter1>

1. first section
2. second section
3. third section
4. fourth section

and so on. Suppose one chapter1 element is removed in between, lets say
second section, then the numbering should reset itself so that now the
output looks like:

1. first section
2. third section
3. fourth section