Calculation: -(1/2)+(1/6)+(1/12)+(1/20)+(1/30)+(1/42)+(1/56).
计算：-(1/2)+(1/6)+(1/12)+(1/20)+(1/30)+(1/42)+(1/56)．
<gadget id="calculator">1 / 8</gadget>
<output>1/8 = around 0.125</output>

<result>1/8 = around 0.125</result>