/*
2"S5+ as 8 x 8 matrices over Z.
Rep 2ab + 2ab.
*/

F:=RationalField();

G<x,y>:=MatrixGroup<8,F|\[
0,1,0,0,0,0,0,0,
1,0,0,0,0,0,0,0,
0,0,0,1,0,0,0,0,
0,0,1,0,0,0,0,0,
0,0,0,0,0,1,0,0,
0,0,0,0,1,0,0,0,
0,0,0,0,0,0,0,1,
0,0,0,0,0,0,1,0]
,\[
0,0,1,0,0,0,-1,0,
0,0,0,-1,0,1,0,1,
0,0,0,0,0,0,1,0,
0,0,0,0,0,0,-1,-1,
-1,1,0,1,0,-1,0,0,
-1,0,-1,0,0,0,0,0,
0,0,0,0,0,1,0,0,
0,0,1,0,-1,0,-1,0]
>;

C:=x;D:=y;