2012-2011+2010-2009+...+4-3+2-1=how much.
2012-2011+2010-2009+…+4-3+2-1=多少．
<gadget id="calculator">4 - 3</gadget>
<output>1</output>

<gadget id="calculator">2 - 1</gadget>
<output>1</output>

<gadget id="calculator">1 + 1</gadget>
<output>2</output>

<gadget id="calculator">2_012 / 2</gadget>
<output>1_006</output>

<gadget id="calculator">1 * 1_006</gadget>
<output>1_006</output>

<result>1_006</result>