Process a batch of hats, 1000 hats have been processed, accounting for (1/5) of the total. How many tops have not been processed.
加工一批帽子，已加工1000顶，占总数的(1/5)．还有多少顶没加工．
<gadget id="calculator">1 / 5</gadget>
<output>1/5 = around 0.2</output>

<gadget id="calculator">1_000 / (1/5)</gadget>
<output>5_000</output>

<gadget id="calculator">5_000 - 1_000</gadget>
<output>4_000</output>

<result>4_000</result>