c an ALC problem
p cnf 7 12
-1 0
2 0
3 -4 -1 0
5 -6 -7 0
1 -2 -3 0
1 -2 -5 0
7 -2 -3 0
7 -2 -5 0
1 -2 6 0
7 -2 6 0
1 -2 7 0
-2 7 0