How many four-digit numbers can be formed with 10 numbers from 0 to 9 without repeating numbers?
用0～9这10个数字可以组成多少个没有重复数字的四位数．
<gadget id="calculator">9 * 9 * 8 * 7</gadget>
<output>4_536</output>

<result>4_536</result>