If a rope is 1 meter long and forms a rectangle with a length of 30 cm and a width of 10 cm, how many centimeters are left?
一根绳子长1米，围成一个长30厘米，宽10厘米的长方形后，还剩多少厘米．
<gadget id="calculator">1 * 100</gadget>
<output>100</output>

<gadget id="calculator">30 + 10</gadget>
<output>40</output>

<gadget id="calculator">40 * 2</gadget>
<output>80</output>

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

<result>20</result>