(1/(1*2))+(1/(2*3))+(1/(3*4))+(1/(4*5))+…+(1/(1999*2000) ).
(1/(1*2))+(1/(2*3))+(1/(3*4))+(1/(4*5))+…+(1/(1999*2000))．
<gadget id="calculator">1 / 2_000</gadget>
<output>1/2_000 = around 0.0005</output>

<gadget id="calculator">1 - (1/2_000)</gadget>
<output>1_999/2_000 = around 0.9995</output>

<result>1_999/2_000 = around 0.9995</result>