It is known that there are 50 students in a certain class, 28 students in the mathematics group, 22 students in the language group, and 26 students in the English group. 8 people participated in the mathematics and Chinese groups at the same time, 7 people participated in the Chinese and English groups at the same time, 16 people participated in the mathematics and English groups at the same time, and 1 person participated in all three groups. So how many people did not participate in the three groups?
已知某班有50名学生，参加数学小组28人，参加语文小组22人，参加英语小组26人．同时参加数学、语文小组的8人，同时参加语文、英语小组的7人，同时参加数学、英语小组的16人，三个小组都参加的l人．那么三个小组都不参加的有多少人．
<gadget id="calculator">8 + 7 + 16</gadget>
<output>31</output>

<gadget id="calculator">26 - 31</gadget>
<output>-5</output>

<gadget id="calculator">28 + 22 + (-5) + 1</gadget>
<output>46</output>

<gadget id="calculator">50 - 46</gadget>
<output>4</output>

<result>4</result>