A piece of rectangular drawing paper with a length of 21 centimeters and a width of 11 centimeters, with a margin of 1 centimeter around, how many square centimeters is the area of the painting part in the middle?
一张长是21厘米，宽是11厘米的长方形画纸，四周留出1厘米的空白，中间的作画部分面积是多少平方厘米？
<gadget id="calculator">1 * 2</gadget>
<output>2</output>

<gadget id="calculator">21 - 2</gadget>
<output>19</output>

<gadget id="calculator">11 - 2</gadget>
<output>9</output>

<gadget id="calculator">19 * 9</gadget>
<output>171</output>

<result>171</result>