paper mill produces 2,000 tons of paper in 100 days. At the beginning, it can only produce 10 tons of paper per day. In the middle stage, due to improved technology, the daily output has doubled. In the final stage, due to the purchase of new equipment, the daily output has increased by one and a half times compared with the middle stage. It is known that the number of production days in the middle stage is twice that of the initial stage and 13 days more, so how many days are there in the final stage?
某造纸厂在100天里共生产2000吨纸，开始阶段，每天只能生产10吨纸．中间阶段由于改进了技术，每天的产量提高了一倍．最后阶段由于购置了新设备，每天的产量又比中间阶段提高了一倍半．已知中间阶段生产天数的2倍比开始阶段多13天，那么最后阶段有几天？
<gadget id="calculator">13 / 2</gadget>
<output>13/2 = around 6.5</output>

<gadget id="calculator">100 - (13/2)</gadget>
<output>187/2 = around 93.5</output>

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

<gadget id="calculator">3 / 1 / 2</gadget>
<output>3/2 = around 1.5</output>

<gadget id="calculator">1 + 3 + (3/2)</gadget>
<output>11/2 = around 5.5</output>

<gadget id="calculator">(187/2) / (11/2)</gadget>
<output>17</output>

<result>17</result>