Simple calculation: 2009*2008-2008*2007+2007*2006-2006*2005+2005*2004-2004*2003.
简便计算：2009*2008-2008*2007+2007*2006-2006*2005+2005*2004-2004*2003．
<gadget id="calculator">2_009 * 2_008</gadget>
<output>4_034_072</output>

<gadget id="calculator">2_008 * 2_007</gadget>
<output>4_030_056</output>

<gadget id="calculator">4_034_072 - 4_030_056</gadget>
<output>4_016</output>

<gadget id="calculator">2_007 * 2_006</gadget>
<output>4_026_042</output>

<gadget id="calculator">2_006 * 2_005</gadget>
<output>4_022_030</output>

<gadget id="calculator">4_026_042 - 4_022_030</gadget>
<output>4_012</output>

<gadget id="calculator">2_005 * 2_004</gadget>
<output>4_018_020</output>

<gadget id="calculator">2_004 * 2_003</gadget>
<output>4_014_012</output>

<gadget id="calculator">4_018_020 - 4_014_012</gadget>
<output>4_008</output>

<gadget id="calculator">4_016 + 4_012 + 4_008</gadget>
<output>12_036</output>

<result>12_036</result>