Teacher Li conducted a small talent survey on some students. The result of the survey is: 22 people can play the clarinet, 8 people can play the violin, and 4 people can play both the clarinet and the violin. The surveyed students knew at least one of the musical instruments. How many students did Mr. Li investigate?
李老师对一些同学进行才艺小调查，调查的结果是：会吹竖笛的有22人，会拉小提琴的有8人，其中既会吹竖笛又会拉小提琴的有4人．被调查的同学至少会其中一种乐器．李老师调查了多少名同学？
<gadget id="calculator">8 - 4</gadget>
<output>4</output>

<gadget id="calculator">22 + 4</gadget>
<output>26</output>

<result>26</result>