# possible stops: 4,6,8
# f: f(x). g: F(x).

flist=F(x),-F(x),F(-x),-F(-x),	F(x+1),F(x-1),F(x/2),-F(x/2)
xlist=t,t,-t,-t,		t-1,t+1,2*t,2*t
ylist=g,-g,g,-g,		g,g,g,-g

