To build a road, on the first day (1/2) of this road is repaired, there is 2 kilometers more, on the second day, the remaining (1/3) is repaired by 1 kilometer, and on the third day, the rest of the road (1/3) is repaired on the second day (1 /4) 1 kilometer more. In this way, there are still 20 kilometers left to be repaired. Find the length of this road?
修一条路，第一天修这条路的(1/2)还多2千米，第二天修余下的(1/3)少1千米，第三天修第二天余下的(1/4)还多1千米．这样还剩下20千米没有修完．求这条路的长度？
<gadget id="calculator">20 + 1</gadget>
<output>21</output>

<gadget id="calculator">1 / 4</gadget>
<output>1/4 = around 0.25</output>

<gadget id="calculator">1 - (1/4)</gadget>
<output>3/4 = around 0.75</output>

<gadget id="calculator">21 / (3/4)</gadget>
<output>28</output>

<gadget id="calculator">28 - 1</gadget>
<output>27</output>

<gadget id="calculator">1 / 3</gadget>
<output>1/3 = around 0.333333</output>

<gadget id="calculator">1 - (1/3)</gadget>
<output>2/3 = around 0.666667</output>

<gadget id="calculator">27 / (2/3)</gadget>
<output>81/2 = around 40.5</output>

<gadget id="calculator">(81/2) + 2</gadget>
<output>85/2 = around 42.5</output>

<gadget id="calculator">1 / 2</gadget>
<output>1/2 = around 0.5</output>

<gadget id="calculator">1 - (1/2)</gadget>
<output>1/2 = around 0.5</output>

<gadget id="calculator">(85/2) / (1/2)</gadget>
<output>85</output>

<result>85</result>