# This example was contributed by Michael Claßen <michael.classen@gmail.com>
P :=
6 7
   0    1    0    0    0   -1    1
   0    0    0 5000    0   -3    8
   0    0    0    0 5000   -1    4
   1    0    1    0    0    0    0
   1    0    0    0    0    1   -4
   1    0    0    0    0    0    1
;
assert((card P) = { });
