When the third graders go on a spring outing, each of them brings at least one piece of milk and juice. 84 people took milk, 77 people took juice, and 39 people took both. How many people in the third grade went to the spring outing?
三年级学生去春游，牛奶和果汁每人至少带一样．带牛奶的有84人，带果汁的有77人，两样都带的有39人．三年级共有多少人去春游？
<gadget id="calculator">77 - 39</gadget>
<output>38</output>

<gadget id="calculator">84 + 38</gadget>
<output>122</output>

<result>122</result>