import java.util.Scanner;

public class RecursionDemo2
{
    public static void main(String[] args)
    {
         System.out.println("Enter a nonnegative number:");
         Scanner keyboard = new Scanner(System.in);
         int number = keyboard.nextInt( );
         System.out.println(number + " contains " +
							getNumberOfZeros(number) + " zeros.");
    }

    /**
     Precondition: n >= 0
     Returns the number of zero digits in n.
    */
    public static int getNumberOfZeros(int n)
    {
		int result;
		
        if (n == 0)
            result = 1;
        else if (n < 10) 
            result = 0;  //n has one digit that is not 0
        else if (n % 10 == 0)
            result = getNumberOfZeros(n / 10) + 1;
        else //n % 10 != 0
            result = getNumberOfZeros(n / 10);
			
		return result;
    }
}