c an ALC problem
p cnf 6 13
-1 -2 3 4 0
-1 -2 5 4 0
-6 -2 3 4 0
-6 -2 5 4 0
2 -4 4 0
-2 4 0
6 -2 2 0
6 4 2 0
2 -2 0
2 4 0
-3 -2 2 0
-3 4 2 0
-4 0