Well done! That's the right answer.
Hint



+
-------------
0
1
2
3
4
5
6
7
8
+
-------------
0
1
2
3
4
5
6
7
8
+
-------------
0
1
2
3
4
5
6
7
8
+
-------------
0
1
2
3
4
5
6
7
8