Who walks on the sand that on the beach?
The boy walks on the sand.
    src        edge_attr  dst
0     0  to the right of    6
1     0  to the right of    7
2     0  to the right of   10
3     0  to the right of    9
4     0       walking on    5
5     2  to the right of    5
6     5   to the left of   16
7     5   to the left of   13
8     5   to the left of    2
9     5               on   14
10    6   to the left of    0
11    7   to the left of    0
12    9   to the left of    0
13   10   to the left of    0
14   13  to the right of    5
15   15       walking on   14
16   16      standing on   14
17   16  to the right of    5