What is the ladder on?
The ladder is on the island.
    src        edge_attr  dst
0     1  to the right of   11
1     1   to the left of   19
2     1   to the left of   12
3     1   to the left of    8
4     1  to the right of    5
5     2   to the left of   13
6     2   to the left of    3
7     2  to the right of   18
8     2               on    9
9     2   to the left of   11
10    3  to the right of    2
11    3  to the right of    9
12    3   to the left of   13
13    3  to the right of   18
14    5   to the left of    1
15    5               on   15
16    6  to the right of   13
17    6  to the right of   11
18    7  to the right of   17
19    7  to the right of   10
20    7   to the left of   13
21    8  to the right of    1
22    9   to the left of   13
23    9   to the left of   11
24    9   to the left of    3
25   10   to the left of   13
26   10  to the right of   17
27   10   to the left of    7
28   11  to the right of    2
29   11  to the right of    9
30   11   to the left of   14
31   11  to the right of   18
32   11   to the left of    1
33   11   to the left of    6
34   11  to the right of   17
35   11               in   14
36   12  to the right of    1
37   13  to the right of    7
38   13  to the right of   10
39   13  to the right of    2
40   13  to the right of    9
41   13   to the left of   14
42   13  to the right of   17
43   13   to the left of    6
44   13  to the right of    3
45   14  to the right of   11
46   14  to the right of   13
47   16  to the right of   18
48   17   to the left of   11
49   17   to the left of   10
50   17   to the left of    7
51   17   to the left of   13
52   18   to the left of    2
53   18   to the left of   11
54   18   to the left of   16
55   18   to the left of    3
56   19  to the right of    1