If a rope is wrapped around the pillar twice, the rope will be 40 cm longer, and if it is wound three times around the pillar, the rope will be 20 cm shorter. How long is this rope?
用一根绳子绕柱子2圈则绳子多40厘米，如果绕柱子3圈则绳子少20厘米．这根绳子有多长？
<gadget id="calculator">40 + 20</gadget>
<output>60</output>

<gadget id="calculator">3 - 2</gadget>
<output>1</output>

<gadget id="calculator">60 / 1</gadget>
<output>60</output>

<gadget id="calculator">60 * 2</gadget>
<output>120</output>

<gadget id="calculator">120 + 40</gadget>
<output>160</output>

<result>160</result>