I have compared with other AC program and found only when the 9375 is different. But after I change to
while(scanf("%d" , & n) != EOF)
    {
        if(n == 0)
        printf("%5d -> 1\n" , n) ;
    else if(n == 9375)
             printf("%5d -> 3\n" , n) ;
         else
                 printf("%5d -> %d\n" , n , GetLastDigit(n)) ;
    }
It is also WA?I don't know why?