Which material is the ground made of?
The ground is made of cement.
    src        edge_attr  dst
0     0  to the right of    2
1     0  to the right of    1
2     0   to the left of    3
3     0          worn on    7
4     1   on the side of    2
5     1   to the left of    0
6     1   to the left of    7
7     2   to the left of    7
8     2   to the left of    6
9     2   to the left of    0
10    2   to the left of    9
11    2   to the left of    5
12    2   to the left of    3
13    3  to the right of    5
14    3  to the right of    6
15    3  to the right of    2
16    3  to the right of    7
17    3  to the right of    0
18    4   on the side of    3
19    5  to the right of    6
20    5  to the right of    2
21    5   to the left of    3
22    6   to the left of    3
23    6  to the right of    2
24    6   to the left of    5
25    7  to the right of    2
26    7  to the right of    1
27    7   to the left of    3
28    9  to the right of    2
29    9          worn on    7