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