A deadly Duck Number

import java .io.*;
class DuckNumber
{
    public static void main()throws IOException
    {
        BufferedReader br=new BufferedReader
            (new InputStreamReader(System.in));
        System.out.println("Enter a no.");
        int num =Integer.parseInt(br.readLine());
        boolean first=false;
        boolean flag=false;
        int rem=0;
        while(num!=0)
        {
            rem=num%10;
            num=num/10;
            if(rem==0)
                flag=true;
        }
        if(rem==0)
        {
            first=true;
        }
        if(flag==true&&first==false)
        {
            System.out.println("Duck Number");
        }
        else 
        {
            System.out.println("Not a Duck number");
        }

    }
}