c d = 7
c n = 21
c p = 56
c r = 3
p cnf 21 56
13 14 1 0
-13 -14 1 0
13 -14 -1 0
-13 14 -1 0
1 15 2 0
-1 -15 2 0
1 -15 -2 0
-1 15 -2 0
2 16 3 0
-2 -16 3 0
2 -16 -3 0
-2 16 -3 0
3 17 4 0
-3 -17 4 0
3 -17 -4 0
-3 17 -4 0
4 18 5 0
-4 -18 5 0
4 -18 -5 0
-4 18 -5 0
5 19 6 0
-5 -19 6 0
5 -19 -6 0
-5 19 -6 0
6 20 21 0
-6 -20 21 0
6 -20 -21 0
-6 20 -21 0
7 20 21 0
-7 -20 21 0
7 -20 -21 0
-7 20 -21 0
8 19 7 0
-8 -19 7 0
8 -19 -7 0
-8 19 -7 0
9 18 8 0
-9 -18 8 0
9 -18 -8 0
-9 18 -8 0
10 17 9 0
-10 -17 9 0
10 -17 -9 0
-10 17 -9 0
11 16 10 0
-11 -16 10 0
11 -16 -10 0
-11 16 -10 0
12 15 11 0
-12 -15 11 0
12 -15 -11 0
-12 15 -11 0
13 14 -12 0
-13 -14 -12 0
13 -14 12 0
-13 14 12 0