There are 500 students in the fourth, fifth and sixth grades in a certain school, including 138 students in the sixth grade, 162 students in the fifth grade, and how many students in the fourth grade?
某学校四、五、六年级共有500人，其中六年级有138人，五年级有162人，四年级有多少人？
<gadget id="calculator">500 - 138 - 162</gadget>
<output>200</output>

<result>200</result>