There is a row of 100 trees on the embankment. Counting from left to right, the 78th tree is planted in one shift to the right; counting from right to left, the 67th tree is planted in three shifts to the left; It is the second class. How many trees did the second class plant?
河堤上有一排树共100棵，从左往右数，第78棵起往右都是一班种的；从右往左数，第67棵起往左都是三班种的；其余都是二班种的．二班种了多少棵．
<gadget id="calculator">67 - 100 - 2</gadget>
<output>-35</output>

<gadget id="calculator">78 + (-35)</gadget>
<output>43</output>

<result>43</result>