p cnf 20 7
  1 3 5 7 9 11 13 15 17 19
  1 4 7 10 13 16 19
  1 6 11 16
  1 8 15
  1 12
  1 14
  1 18

c a correct solution is: 0 0 0 0 0 0 0 0 0 0 0 1 0 1 1 1 0 1 0 0