|x|=5, |y|=1, then ||xy|-|x+y||=how much.
|x|=5，|y|=1，那么||x-y|-|x+y||=多少．
<gadget id="calculator">5 + 1</gadget>
<output>6</output>

<gadget id="calculator">5 - 1</gadget>
<output>4</output>

<gadget id="calculator">6 - 4</gadget>
<output>2</output>

<result>2</result>