In the grade mathematics interest group, there are 25 students who are not in the fourth grade, 26 people who are not in the fifth grade, and a total of 33 people in the fourth and fifth grades participate in the mathematics interest group. How many people participated in the school mathematics interest group?
年级数学兴趣小组中，有25人不是四年级的学生，有26人不是五年级的学生，四、五年级参加数学兴趣小组的共有33人．参加学校数学兴趣小组的共有多少人？
<gadget id="calculator">26 - 33</gadget>
<output>-7</output>

<gadget id="calculator">25 + (-7)</gadget>
<output>18</output>

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

<gadget id="calculator">9 + 33</gadget>
<output>42</output>

<result>42</result>