Choose 1 staple food and 3 dishes for lunch from 10 staple foods and 20 dishes. How many combinations are there?
从10种主食和20种菜肴中选取1种主食和3种菜肴作为午餐，共有多少种搭配方法？
<gadget id="calculator">20 * 19 * 18</gadget>
<output>6_840</output>

<gadget id="calculator">3 * 2 * 1</gadget>
<output>6</output>

<gadget id="calculator">6_840 / 6</gadget>
<output>1_140</output>

<gadget id="calculator">10 * 1_140</gadget>
<output>11_400</output>

<result>11_400</result>