A rope, cut off half and 1 cm for the first time, cut off the remaining half and 1 cm for the second time, and cut off the remaining half and 1 cm for the third time, leaving 7 cm. How many centimeters was this rope originally?
一根绳子，第一次截去一半零1厘米，第二次截掉剩下的一半零1厘米，第三次截掉再剩下的一半零1厘米，还剩下7厘米．这根绳子原来长多少厘米？
<gadget id="calculator">7 + 1</gadget>
<output>8</output>

<gadget id="calculator">8 * 2</gadget>
<output>16</output>

<gadget id="calculator">16 + 1</gadget>
<output>17</output>

<gadget id="calculator">17 * 2</gadget>
<output>34</output>

<gadget id="calculator">34 + 1</gadget>
<output>35</output>

<gadget id="calculator">35 * 2</gadget>
<output>70</output>

<result>70</result>