(1/(1986*1987))+(1/(1987*1988))+(1/(1988*1989))+...+(1/(1992*1993)).
(1/(1986*1987))+(1/(1987*1988))+(1/(1988*1989))+…+(1/(1992*1993))．
<gadget id="calculator">1 / 1_992</gadget>
<output>1/1_992 = around 0.000502</output>

<gadget id="calculator">1 / 1_993</gadget>
<output>1/1_993 = around 0.000502</output>

<gadget id="calculator">(1/1_992) - (1/1_993)</gadget>
<output>1/3_970_056 = around 0</output>

<result>1/3_970_056 = around 0</result>