There are 10 trees in a row, each of which is 10 meters apart. There is a well at the first tree. Uncle Zhang pours two buckets of water to shower 2 trees at a time. How far must he walk to finish the 10 trees? rice.
排成一行的10棵树，每棵相隔10米，在第一棵树处有一口水井，张叔叔每次打两桶水淋2棵树，要淋完这10棵树，他至少要走多少米．
<gadget id="calculator">2 - 1</gadget>
<output>1</output>

<gadget id="calculator">10 * 1 * 2</gadget>
<output>20</output>

<gadget id="calculator">4 - 1</gadget>
<output>3</output>

<gadget id="calculator">10 * 3 * 2</gadget>
<output>60</output>

<gadget id="calculator">6 - 1</gadget>
<output>5</output>

<gadget id="calculator">10 * 5 * 2</gadget>
<output>100</output>

<gadget id="calculator">8 - 1</gadget>
<output>7</output>

<gadget id="calculator">10 * 7 * 2</gadget>
<output>140</output>

<gadget id="calculator">10 - 1</gadget>
<output>9</output>

<gadget id="calculator">10 * 9</gadget>
<output>90</output>

<gadget id="calculator">20 + 60 + 100 + 140 + 90</gadget>
<output>410</output>

<result>410</result>