wrong answer on test 1
input:27
expected:18
1 9
2 8
3 7
4 6
5 5
6 4
7 3
8 2
9 1
10 17
11 16
12 15
13 14
14 13
15 12
16 11
17 10
27 27
found:18
1 9
9 1
2 8
8 2
3 7
7 3
4 6
6 4
10 17
17 10
11 16
16 11
12 15
15 12
13 14
14 13
5 5
18 18