function [X, f1] = DeJong8(Xi)
n = 10;
i = 0;
b = 0;
LL = -600;              %Lower limit
UL = 600;               %Upper limit
X = LL + rand(1,n)*(UL - LL);% step1 Choose starting design X, 
for i = 1:1:10
    b = b*cos(X(i)./(i.^0.5));
end
    f1 = 1 + sum(((X(i).^2)./4000) - b);
end