There are 42 students in class 1 of the third grade who subscribe to "Youth Daily", 31 students subscribe to "Fairy Tale Newspaper", and each of them subscribes to at least one of the newspapers. How many students subscribe to "Youth Daily" and Subscribe to "Fairy Tale Newspaper"?
三年级1班有42名同学订阅《少年报》的有31名同学，订阅《童话报》的有27名同学，每人至少订其中一份报纸，有多少名同学既订《少年报》又订《童话报》？
<gadget id="calculator">27 - 42</gadget>
<output>-15</output>

<gadget id="calculator">31 + (-15)</gadget>
<output>16</output>

<result>16</result>