function dy = grass(t,y);
dy = zeros(3,1);
dy(1) = y(1) - y(2)*y(1) - y(1)*y(1)-y(3)*y(1);
dy(2) =  y(1)*y(2) - .2*y(2);
dy(3) = -.1*y(3) + .5*

y(1)*y(3);