<?xml version="1.0" encoding="UTF-8"?>
<xsl:stylesheet version="1.0"
				xmlns:xsl="http://www.w3.org/1999/XSL/Transform"
				>
<xsl:template match="math">
<math>
	<xsl:apply-templates select="add"></xsl:apply-templates>
	<xsl:apply-templates select="neg"></xsl:apply-templates>
</math>
</xsl:template>

<xsl:template match="add">
	<num><xsl:value-of select="sum(num)" /></num>
</xsl:template>

<xsl:template match="neg">
	<num><xsl:value-of select="-sum(num)" /></num>
</xsl:template>

</xsl:stylesheet>