Calculate with a simple method: 2001*2002-2000*2003.
用简便方法计算：2001*2002-2000*2003．
<gadget id="calculator">2_001 * 2_002</gadget>
<output>4_006_002</output>

<gadget id="calculator">2_000 * 2_003</gadget>
<output>4_006_000</output>

<gadget id="calculator">4_006_002 - 4_006_000</gadget>
<output>2</output>

<result>2</result>