How long is this surfboard?
The surfboard is long.
    src        edge_attr  dst
0     0   to the left of   10
1     0   to the left of    1
2     0   to the left of    6
3     1   to the left of   10
4     1  to the right of    2
5     1  to the right of    0
6     2   to the left of   10
7     2   to the left of    1
8     2   to the left of    6
9     4               on   10
10    6  to the right of    0
11    6  to the right of    2
12    8          wearing    6
13    8        riding on   10
14    8               on   10
15   10               in    7
16   10  to the right of    0
17   10  to the right of    2
18   10  to the right of    1