There are 5 balls numbered 1, 2, 3, 4, 5 and 5 boxes numbered 1, 2, 3, 4, 5. Each box is required to have one and only one ball, but each box is small Both the ball and the box have different numbers. Try to determine how many different ways there are.
有5个编号为1，2，3，4，5的小球和5个编号为1，2，3，4，5的盒子，要求每个盒子有且只有一个小球，但每个盒子中小球和盒子编号都不同，试确定共有多少种不同的放法．
<gadget id="calculator">5 * 4 * 3 * 2 * 1</gadget>
<output>120</output>

<gadget id="calculator">10 * 2</gadget>
<output>20</output>

<gadget id="calculator">5 * 9</gadget>
<output>45</output>

<gadget id="calculator">120 - 1 - 10 - 20 - 45</gadget>
<output>44</output>

<result>44</result>