There are 55 students in Class 3 and 1, each of whom participates in at least one of running and rope skipping competitions. It is known that 36 people participated in the race and 38 people participated in the rope skipping. How many people participated in both competitions?
三1班有学生55人，每人至少参加赛跑和跳绳比赛中的一种．已知参加赛跑的有36人，参加跳绳的有38人．两项比赛都参加的有几人？
<gadget id="calculator">38 - 55</gadget>
<output>-17</output>

<gadget id="calculator">36 + (-17)</gadget>
<output>19</output>

<result>19</result>