GAP 4.8.9 installation with standard packages -- copy to your CoCalc project to get it
#g3 f1 6x6 0 1 0 0 0 0 1 0 0 0 0 0 0 0 1 0 0 0 0 0 0 1 0 0 0 0 0 0 1 0 0 0 0 0 0 1 6x6 -1 0 0 0 0 0 1 1 1 0 0 0 0 -1 0 0 0 0 0 0 0 1 0 0 0 0 0 0 1 0 0 0 0 0 0 1 6x6 0 0 0 1 0 0 0 0 0 0 1 0 0 0 0 0 0 1 1 0 0 0 0 0 0 1 0 0 0 0 0 0 1 0 0 0 6x6 2 1 1 0 0 0 1 2 1 0 0 0 1 1 2 0 0 0 0 0 0 2 1 1 0 0 0 1 2 1 0 0 0 1 1 2 2^9 * 3^2 = 4608 dim6/6-1d