For a bundle of iron wires, the first use of the full length (1/2) is 3m longer, and the second use of the remaining (1/2) is less than 3m. The remaining (1/2) is used for the third time, and there is still 18m left at this time. How many meters is this bundle of iron wires originally?
一捆铁丝，第一次用去全长的(1/2)多3m，第二次用去余下的(1/2)少3m．第三次用去余下的(1/2)，这时还剩下18m，这捆铁丝原来有多少米？
<gadget id="calculator">1 / 2</gadget>
<output>1/2 = around 0.5</output>

<gadget id="calculator">18 / (1/2)</gadget>
<output>36</output>

<gadget id="calculator">36 - 3</gadget>
<output>33</output>

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

<gadget id="calculator">33 / (1/2)</gadget>
<output>66</output>

<gadget id="calculator">66 + 3</gadget>
<output>69</output>

<gadget id="calculator">69 / (1/2)</gadget>
<output>138</output>

<result>138</result>