8. For a natural number $a, S(a)$ denotes the sum of the digits of $a$ (for example, $S(123)=1+2+3=6$ ). If a natural number $n$ has all distinct digits, and $S(3 n)=3 S(n)$, then the maximum value of $n$ is $\qquad$
【Analysis】Q $S(3 n)=3 S(n)$  
$\therefore$ when 3 is multiplied by $n$, there should be no carry-over, so the largest digit in $n$ can only be 3, hence the maximum value of $n$ is 3210.