What is the circumference of a semicircle with a radius of 5 cm?
一个半径为5厘米的半圆，周长应该是多少．
<gadget id="calculator">3.14 * 5</gadget>
<output>15.7</output>

<gadget id="calculator">5 * 2</gadget>
<output>10</output>

<gadget id="calculator">15.7 + 10</gadget>
<output>25.7</output>

<result>25.7</result>