The telephone number of Nantong City has been increased from the original six digits to seven digits. It is stipulated that the first digit cannot be 0, and the rest of the digits can be any one of 0 to 9, and the numbers of different digits can be repeated, so the city can at most How many telephones can be accommodated.
南通市的电话号码由原来的六位数升至七位数，规定首位不能是0，其余各位数上可以是0～9中的任何一个，并且不同位的数字可以重复，那么我市最多可容纳多少部电话机．
<gadget id="calculator">9 * 10 * 10 * 10 * 10 * 10 * 10</gadget>
<output>9_000_000</output>

<result>9_000_000</result>