function [Ydot] = insu18(t,Y)
a=2;b=1;c=1;d=2;e=1;f=0.5;
Ydot(1) = -a*Y(1)+b*Y(2)+c;
Ydot(2) = d*Y(2)-e*Y(1)*Y(2)-f;
Ydot=Ydot';