function F=normlike(theta,e2)
omega=theta(1);
alpha=theta(2);
beta=theta(3);
T=max(size(e2));
s2=zeros(size(e2));
s2(1)=e2(1);
for i=2:T
    s2(i)=omega+alpha*e2(i-1)+beta*s2(i-1);
end

F=0.5*(T-1)*log(2*pi)+0.5*sum(e2(2:T)./s2(2:T))+0.5*sum(s2(2:T));

