In a school, 15 students are absent on Monday, 12 are absent on Tuesday, and 9 are absent on Wednesday. If there are 22 students who are absent for at least one of the three days, how many students are absent at most?
在某学校，星期一有15人缺席，星期二有12人缺席，星期三有9人缺席，如果这三天中至少有一天缺席的学生有22人，那么都缺席的学生最多有几人？
<gadget id="calculator">9 - 22</gadget>
<output>-13</output>

<gadget id="calculator">15 + 12 + (-13)</gadget>
<output>14</output>

<gadget id="calculator">1 - 1</gadget>
<output>0</output>

<gadget id="calculator">1 + 1 + 0</gadget>
<output>2</output>

<gadget id="calculator">14 / 2</gadget>
<output>7</output>

<result>7</result>