If a circle is surrounded by a wire with a diameter of 16 cm, if it is used to form a square, what is the side length of the square?
用一根直径是16厘米的铁丝围成一个圆，如果用它围成一个正方形，这个正方形的边长是多少厘米？
<gadget id="calculator">16 / 4</gadget>
<output>4</output>

<gadget id="calculator">3.14 * 4</gadget>
<output>12.56</output>

<result>12.56</result>