2007*2006-2006*2005+2005*2004-2004*2003+2003*2002-2002*2001=how many.
2007*2006-2006*2005+2005*2004-2004*2003+2003*2002-2002*2001=多少．
<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">2_003 * 2_002</gadget>
<output>4_010_006</output>

<gadget id="calculator">2_002 * 2_001</gadget>
<output>4_006_002</output>

<gadget id="calculator">4_010_006 - 4_006_002</gadget>
<output>4_004</output>

<gadget id="calculator">4_012 + 4_008 + 4_004</gadget>
<output>12_024</output>

<result>12_024</result>