function dxy = gy4_egy(t,xy)
dxy = zeros(2,1); %kimenet [dx, dy]
x=xy(1);
y=xy(2);
%egyenletek: stabil pont:        dx=x*(1-x/2-y); dy=y*(-1-y+x);
%            periodikus pályák:  dx=x*(1/3-y); dy=y*(-4/3+x);

dxy(1) = x*(1/3-y);
dxy(2) = y*(-4/3+x);

%dxy(1)=x*(1-x/2-y); 
%dxy(2)=y*(-1-y+x);
end