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class XOException extends RuntimeException {

	private static final long serialVersionUID = 1L;
	
	public XOException(String message) {
		super(message);
	}
}

class XO extends XOInterface {
	private int moves;
	
	public XO() {
		super();
		this.moves = 0;
	}
	
	@Override
	public void start(){
		if(getPlayer() > 0)
			throw new XOException("Game already started");
		setPlayer(1);
	}
	
	@Override
	public boolean play(int field){
		boolean win;
		int player = getPlayer();
		if(field < 0 || field > 8)
			throw new XOException("Invalid field");
		if(getFields()[field] > 0)
			throw new XOException("Field already taken");
		if(player == 0)
			throw new XOException("Game not started");
					
		win = setField(field, player);
		moves += 1;
		
		if(win) {
			stop();
		}else if (moves == 9){
			stop();
		}else{
			setPlayer((2*player) % 3);
		}
		return win;
	}
	
	@Override
	public void stop(){
		if(getPlayer() == 0)
			throw new XOException("Game already stopped");
		resetFields();
		setPlayer(0);
		moves = 0;
	}	
}