//NumberOfZeros.java

import java.util.Scanner;

public class NumberOfZeros
{
    public static void main(String[] args)
    {
        System.out.print("\nEnter a nonnegative integer: ");
        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;
    }
}