Generating Sequential IDs

Hi,
I want to generate the sequence ids for all the nodes in the xml tree. For
example
my source xml looks like this..
	<A>
		<B></B>
		<C>
			<D></D>
		</C>
		<E>
			<F>
				<G></G>
			</F>
		</E>
	</A>

I want the output xml like..

	<A id=1>
		<B id=2></B>
		<C id=3>
			<D id=4></D>
		</C>
		<E id=5>
			<F id=6>
				<G id=8></G>
			</F>
		</E>
	</A>

Can any one give me the xslt code for this..

Thanks,
Laxmi Narayana Babu
OSI Technologies.