JAVA Help

import java.util.*;
class duck
{
    public static void main()
    {
        Scanner s=new Scanner(System.in);
        int n,a,sum=0;
        n=s.nextInt();
        while (n>0)
        {
            a=n%10;
            if (a==0)
            sum++;
            n=n/10;
        }
        if (sum>0)
        System.out.println("duck no.");
        else
        System.out.println("not duck no.");
    }
}