Spotify Puzzle has me... puzzled

Hello peeps again. I feel like I've been asking a lot of questions. I'm new to this forum so if there's any thing I'm doing wrong please let me know. But here's my dilemma. I'm trying to solve this problem located on the spotify website:

http://www.spotify.com/se/jobs/tech/ticket-lottery/


It's very interesting. I finally got all the code up for it, and it seems like I am getting the right answer. But when I submit the code, they tell me it's wrong. Here's my code:

import java.io.BufferedReader;
import java.io.IOException;
import java.util.ArrayList;
import java.io.InputStreamReader;

/**
 * 
 * @author Rechee Jozil
 * Written 12/26/2012
 */


public class Internship {
	
	
	public static void main(String[] args) throws IOException{
		
		double denomenator = 0.0,  numerator = 0.0, probability = 0.0, pEntered = 0.0, winners = 0.0, tickets = 0.0, pGroup = 0.0;
		BufferedReader r = new BufferedReader(new InputStreamReader(System.in));
		
		//Array list to hold values.
		ArrayList<Double> lotteryInput = new ArrayList<Double>();


		//Add values entered from input stream to arraylist
		System.out.println("Enter values");
		
		//Split string up
		String[] st = r.readLine().split(" ");
		
		//Parse each element in st into double
		for(int i = 0; i < 4 ; i++){
				lotteryInput.add(Double.parseDouble(st[i]));
		}
		r.close();

		//Value checking
		while(lotteryInput.get(0) < 1 || lotteryInput.get(0) > 1000){
			System.out.println("Number of people in lottery cannot be less than 1 or more than 100. Enter number of people in lottery again.");
			Double.parseDouble(r.readLine());
			lotteryInput.set(0, pEntered);
	
		}
		while(lotteryInput.get(1) < 1 || lotteryInput.get(1) > lotteryInput.get(0)){
			System.out.println("Number of winners cannot be less than 1 or greater than number of people in lottery. Enter number of winners again.");
			Double.parseDouble(r.readLine());
			lotteryInput.set(1, winners);
		}
		while(lotteryInput.get(2) < 1 || lotteryInput.get(2) > 100){
			System.out.println("Number of tickets cannot be less than 1 or greater than 100. Enter numbef of tickets again. ");
			Double.parseDouble(r.readLine());
			lotteryInput.set(2, tickets);
		}
		while(lotteryInput.get(3) < 1 || lotteryInput.get(3) > lotteryInput.get(0)){
			System.out.println("Number of people in your group cannot be less than 1 or greater than number of people that entered. Enter number of people in group again. ");
			Double.parseDouble(r.readLine());
			lotteryInput.set(3, pGroup);
		}
		
		//Close buffer 
		r.close();
	
		pEntered = lotteryInput.get(0);
		winners = lotteryInput.get(1);
		tickets = lotteryInput.get(2);
		pGroup = lotteryInput.get(3);
		
		//Main for loop for calculation of probablility
		for(int k = 1; k <= pGroup; k++){
		denomenator = (double) (factorial(pEntered) / (double) (factorial(winners) * factorial(pEntered - winners)));
		numerator = (double) (factorial(pGroup)/ (double) ((factorial(k) * factorial(pGroup - k))) * (double) ((factorial(pEntered - pGroup)) / (double) (factorial(winners - k) * factorial((pEntered - pGroup)- (winners - k)))));
		probability =probability + ((numerator/ denomenator) * TicketProb(pGroup, k, tickets));
		}
		
		System.out.println(probability);
		
	
		
	}
	
	// static recursive factorial method
	 static double factorial(double n){
		if (n == 0){
			return 1;
		}else{
			return n * factorial(n-1);
		}

	}
	 
	 static double TicketProb(double x, double y, double z){
		 if(x <= (y * z)){
			 return 1.0;
		 }
		 else{
			 return 0.0;
		 }
	 }
		 
	 }

If you plug in the sample input given by spotify, my answers are the same. Except with the third sample input where mine is 1.0 and there's is 1.0 with 0 repeating.

I think I've covered all angles. I've edited the code several times with no avail. Any body have any insight on how I might solve this problem?