Calculation: 210+209-208+207-206+...+3-2+1=how much.
计算：210+209-208+207-206+…+3-2+1=多少．
<gadget id="calculator">1 * 104</gadget>
<output>104</output>

<gadget id="calculator">210 + 104 + 1</gadget>
<output>315</output>

<result>315</result>