public List<City> extractNodes(){
		List<City> result = new ArrayList<City>();
		BufferedReader buff = null;
		try{
			File file = new File(problem);
			buff = new BufferedReader(new FileReader(file));
			boolean nodes = false;
			String str;
			while((str = buff.readLine()) != null){
				if(nodes == true && !str.equals("EOF")){
					City city = parseCity(str);
					result.add(city);
				}
				if(str.equals("NODE_COORD_SECTION")){
					nodes = true;
				}
			}
		}catch(FileNotFoundException ex){
			ex.printStackTrace();
		}catch(IOException ex){
			ex.printStackTrace();
		}finally{
			try{
				if(buff != null){
					buff.close();
				}
			}catch(IOException ex){
				ex.printStackTrace();
			}
			
		}
		return result;
	}