What type of material is the gray bench made of?
The bench is made of concrete.
    src        edge_attr  dst
0     0  to the right of    5
1     0   to the left of   13
2     0   to the left of    4
3     1   to the left of    2
4     1  to the right of   19
5     2  to the right of    1
6     2  to the right of   19
7     3   to the left of    8
8     3   to the left of    7
9     4  to the right of    0
10    5   to the left of    0
11    5   to the left of   17
12    5   to the left of   20
13    5   to the left of   13
14    5   to the left of   12
15    6   to the left of    9
16    7  to the right of    3
17    7   to the left of    8
18    8  to the right of   13
19    8  to the right of   12
20    8               on    0
21    8  to the right of    7
22    8  to the right of    3
23    9             near   19
24    9  to the right of    6
25   12  to the right of    5
26   12   to the left of    8
27   13  to the right of    5
28   13  to the right of    0
29   13   to the left of    8
30   17  to the right of    5
31   19          next to    9
32   19   to the left of    2
33   19   to the left of    1
34   19             near    9
35   20  to the right of    5