p cnf 20 75
1       2       3       4       0
5       6       7       8       0
9       10      11      12      0
13      14      15      16      0
17      18      19      20      0
-1      -2      0
-1      -3      0
-1      -4      0
-2      -3      0
-2      -4      0
-3      -4      0
-5      -6      0
-5      -7      0
-5      -8      0
-6      -7      0
-6      -8      0
-7      -8      0
-9      -10     0
-9      -11     0
-9      -12     0
-10     -11     0
-10     -12     0
-11     -12     0
-13     -14     0
-13     -15     0
-13     -16     0
-14     -15     0
-14     -16     0
-15     -16     0
-17     -18     0
-17     -19     0
-17     -20     0
-18     -19     0
-18     -20     0
-19     -20     0
-1      -5      0
-1      -9      0
-1      -13     0
-1      -17     0
-5      -9      0
-5      -13     0
-5      -17     0
-9      -13     0
-9      -17     0
-13     -17     0
-2      -6      0
-2      -10     0
-2      -14     0
-2      -18     0
-6      -10     0
-6      -14     0
-6      -18     0
-10     -14     0
-10     -18     0
-14     -18     0
-3      -7      0
-3      -11     0
-3      -15     0
-3      -19     0
-7      -11     0
-7      -15     0
-7      -19     0
-11     -15     0
-11     -19     0
-15     -19     0
-4      -8      0
-4      -12     0
-4      -16     0
-4      -20     0
-8      -12     0
-8      -16     0
-8      -20     0
-12     -16     0
-12     -20     0
-16     -20     0