A piece of paper subtracts its (1/2) for the first time, and the remaining (1/2) for the second time, how much of this paper is left
一张纸第一次减去它的(1/2)，第二次减去余下的(1/2)，还剩这张纸的多少
<gadget id="calculator">1 / 2</gadget>
<output>1/2 = around 0.5</output>

<gadget id="calculator">1 * (1/2)</gadget>
<output>1/2 = around 0.5</output>

<gadget id="calculator">1 - (1/2)</gadget>
<output>1/2 = around 0.5</output>

<gadget id="calculator">(1/2) * (1/2)</gadget>
<output>1/4 = around 0.25</output>

<gadget id="calculator">1 - (1/2) - (1/4)</gadget>
<output>1/4 = around 0.25</output>

<result>1/4 = around 0.25</result>