A semicircular plastic plate has a radius of 1dm, what is its perimeter in dm?
一个半圆形塑料板，半径是1dm，则它的周长是多少dm．
<gadget id="calculator">3.14 * 1</gadget>
<output>3.14</output>

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

<gadget id="calculator">3.14 + 2</gadget>
<output>5.14</output>

<result>5.14</result>