function S=test(x)
% x0 = [0, 9]
% xo = [0, 0]
% S(xo) = 0

 S=1+(x(1).^2+x(2).^2)/4000-cos(x(1)).*cos(x(2)/sqrt(2));

% 
%   [xo,Ot,nS]=swarm('test29',[3 1],0,[1 1],[-10 10],[10 10],[],100,20)
%