Students from five classes in grade six planted 100 trees in total. It is known that the number of trees planted in each class is different, and the ranking from the most to the least is exactly the first, second, third, fourth, and fifth classes. It is also known that the number of trees planted in the first class is the sum of the number of trees planted in the second and third classes, and the number of trees planted in the second class is the sum of the number of trees planted in the fourth and fifth classes, so how many trees can be planted at most in the third class?
六年级五个班的同学共植树100棵．已知每个班植树的棵数都不相同，且按数量从多到少的排名恰好是一、二、三、四、五班．又知一班植的棵数是二、三班植的棵数之和，二班植的棵数是四、五班植的棵数之和，那么三班最多植树多少棵？
<gadget id="calculator">22 * 3</gadget>
<output>66</output>

<gadget id="calculator">100 - 66</gadget>
<output>34</output>

<gadget id="calculator">34 / 2</gadget>
<output>17</output>

<result>17</result>