10 small trees are planted in a row with a distance of 5 meters. Now we need to water the small trees. It is known that there is a water pipe next to the first small tree, and we can water two trees at a time. How many meters of road.
10棵小树栽成一行，棵距5米．现在要给小树浇水，已知第1棵小树旁有水管，接一次水浇两棵树，如果水管与第1棵树之间的距离忽略不计，浇完所有的小树共要走多少米的路．
<gadget id="calculator">1 * 2</gadget>
<output>2</output>

<gadget id="calculator">3 * 2</gadget>
<output>6</output>

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

<gadget id="calculator">7 * 2</gadget>
<output>14</output>

<gadget id="calculator">9 * 2</gadget>
<output>18</output>

<gadget id="calculator">2 + 6 + 10 + 14 + 18</gadget>
<output>50</output>

<gadget id="calculator">5 * 50</gadget>
<output>250</output>

<result>250</result>