Find: (1986/(1986*1987))+(1986/(1987*1988))+(1986/(1988*1989))+...+(1986/(1999*2000)).
求：(1986/(1986*1987))+(1986/(1987*1988))+(1986/(1988*1989))+…+(1986/(1999*2000))．
<gadget id="calculator">1 / 1_986</gadget>
<output>1/1_986 = around 0.000504</output>

<gadget id="calculator">1 / 2_000</gadget>
<output>1/2_000 = around 0.0005</output>

<gadget id="calculator">(1/1_986) - (1/2_000)</gadget>
<output>7/1_986_000 = around 0.000004</output>

<gadget id="calculator">1_986 * (7/1_986_000)</gadget>
<output>7/1_000 = around 0.007</output>

<result>7/1_000 = around 0.007</result>