package com.yao.Algorithms;

import java.util.HashMap;
import java.util.Map;
/**
 * 
 * @author shuimuqinghua77 @date 2011-11-29
 *
 */
public class Problem15 {
	private static Map<String, Node> seed = new HashMap<String, Node>();
	private static int SIZE = 20;
	private static long sum = 0;

	public static void main(String[] args) {
		seed.put(0 + ":" + 0, new Node(0, 0, 1));
		for (int i = 0; i < SIZE + SIZE; i++) {
			Map<String, Node> map = new HashMap<String, Node>();
			for (Node node : seed.values()) {
				if (node.x == SIZE || node.y == SIZE) {
					sum += node.size;
					continue;
				}
				search(node.x + 1, node.y, node.size, map);
				search(node.x, node.y + 1, node.size, map);
			}
			seed = map;
		}
		System.out.println(sum);
	}

	private static void search(int x, int y, long size, Map<String, Node> map) {
		Node node = new Node(x, y, size);
		String key = x + ":" + y;
		if (map.get(key) != null)
			map.get(key).size += size;
		else
			map.put(key, node);
	}
}

class Node {
	int x;
	int y;
	long size;

	public Node(int x, int y, long size) {
		this.x = x;
		this.y = y;
		this.size = size;
	}
}