public static String cal() {
		boolean hasDot = checkDot();
		boolean Xwon = checkDiagonal('X');
		boolean Owon = checkDiagonal('O');
		
		for(int i = 0; i < 4; i++){
			if(!Xwon) Xwon = checkCol(i, 'X');
			if(!Xwon) Xwon = checkLine(i, 'X');
			if(!Owon) Owon = checkCol(i, 'O');
			if(!Owon) Owon = checkLine(i, 'O');
		}
		
		if(Xwon) return "X won";
		else if(Owon) return "O won";
		else if(hasDot) return "Game has not completed";
		else return "Draw";
	}