The River Management Office plans to desilt the 5,000-meter-long river in 20 days. Due to the effective measures, (1/3) of the whole project was completed in the first 5 days. According to this calculation, how many days can the dredging task be completed in advance?
河道管理处计划用20天时间对长达5000米的河道进行清淤．由于措施得力，结果前5天就完成了全部工程的(1/3)，照这样计算，可以提前几天完成清淤任务？
<gadget id="calculator">1 / 3</gadget>
<output>1/3 = around 0.333333</output>

<gadget id="calculator">5 / (1/3)</gadget>
<output>15</output>

<gadget id="calculator">20 - 15</gadget>
<output>5</output>

<result>5</result>