function f=fun3(k)
z=s+k(1)*y1+k(2)*y2+k(3)*y3;
f(1)=norm(A*x+b*z(2),2);
f(2)=norm(A*(A*x+b*z(2))+b*z(3),2);
f(3)=norm(A*(A*(A*x+b*z(2))+b*z(3))+b*z(4),2);
f(4)=norm(A*(A*(A*(A*x+b*z(2))+b*z(3))+b*z(4))+b*z(5),2);
f(5)=norm(A*(A*(A*(A*(A*x+b*z(2))+b*z(3))+b*z(4))+b*z(5))+b*z(6),2);
end
end