What's the clock on?
The clock is on the tower.
   src        edge_attr  dst
0    0  to the right of    4
1    1  to the right of    3
2    1  to the right of    4
3    2               on    3
4    2  to the right of    4
5    3   to the left of    1
6    4   to the left of    0
7    4   to the left of    2
8    4   to the left of    1