If the circumference of a circle with a radius of 4 cm is equal to the circumference of a square, what is the side length of the square in cm?
半径为4cm的圆的周长和一个正方形的周长相等，则正方形的边长为多少cm．
<gadget id="calculator">4 / 4</gadget>
<output>1</output>

<gadget id="calculator">2 * 3.14 * 1</gadget>
<output>6.28</output>

<result>6.28</result>