private boolean isSolvable(byte[][] board) {
		int counter = 0;
		for (int i = 0; i < SIZE - 1; i++) {
			for (int j = i + 1; j < SIZE; j++) {
				if (board[i/ROW_SIZE][i%ROW_SIZE] > board[j/ROW_SIZE][j%ROW_SIZE]
				       && board[i/ROW_SIZE][i%ROW_SIZE] != 0 
				       && board[j/ROW_SIZE][j%ROW_SIZE] != 0) {
					counter++;
				}
			}
		}
		return (counter%2 == 0);
	}