4
x y z t

x + y + z + t;
x y + y z + z t + t x;
x y z + y z t + z t x + t x y ;
x y z t + 1;;

/* Example by Arnborg and Davenport
** Found in "Experimenting the Grobner basis algorithm with the AIPI system"
**  by Carlo Traverso and Leombattista Donati.
** Proceedings of ISSAC 89.
*/
