x'=px
y'=py
px'=-x-2*x*y
py'=-y-x^2+y^2
aux h=.5*(px*px+py*py)+.5*(x^2+y^2+x^2*y-y^3/3)
aux e=px*px/2+py*py/2+y*y*(1/2-y/3)
init x=0,y=-.1475,px=.3101,py=0
done