A rope is 1 meter long. If a square with a side length of 20 centimeters is formed with this rope, how many centimeters are left on the rope?
一根绳子长1米，用这根绳子围成一个边长20厘米的正方形后，这根绳子还剩下多少厘米．
<gadget id="calculator">1 * 100</gadget>
<output>100</output>

<gadget id="calculator">20 * 4</gadget>
<output>80</output>

<gadget id="calculator">100 - 80</gadget>
<output>20</output>

<result>20</result>