(1/2)+(1/(2+4))+(1/(2+4+6))+...+(1/(2+4+6+...+100)).
(1/2)+(1/(2+4))+(1/(2+4+6))+…+(1/(2+4+6+…+100))．
<gadget id="calculator">1 / 51</gadget>
<output>1/51 = around 0.019608</output>

<gadget id="calculator">1 - (1/51)</gadget>
<output>50/51 = around 0.980392</output>

<result>50/51 = around 0.980392</result>