public static void main(String[] args) {
        if(args.length < 1){
            System.err.println("Usage: java SudokuSolver intput-file.txt");
            System.exit(0);
        }

        Puzzle sudoku = new Puzzle(3);

		try {
			sudoku.populatePuzzle(args[0]);
			System.out.println(sudoku.toString());
			
		    Puzzle solution = colorPuzzle(sudoku);
		    if(solution == null)
			    System.out.println("Sorry! No solution exists :(");
		    else
			    System.out.println("Solved!\n" + solution.toString());
		}
        catch (IOException e){
            System.err.println("Error reading file: " + e.getMessage());
        }
	}