A wire encloses exactly a square with a side length of 30 cm. How long is this wire in centimeters?
一根铁丝恰好围成一个正方形，边长是30厘米．这根铁丝长多少厘米．
<gadget id="calculator">30 * 4</gadget>
<output>120</output>

<result>120</result>