Use an iron plate with a length of 3 meters and a width of 1 meter to make the largest semicircular iron plate. How many square meters of iron plate should be cut off?
用一块长3米，宽1米的铁板做一个最大半圆形铁板，要割去多少平方米铁板？
<gadget id="calculator">3 * 1</gadget>
<output>3</output>

<gadget id="calculator">1 ** 2</gadget>
<output>1</output>

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

<gadget id="calculator">3.14 * (1/2)</gadget>
<output>1.57</output>

<gadget id="calculator">3 - 1.57</gadget>
<output>1.43</output>

<result>1.43</result>