function [ v ] = expvar(a, s, Q, i)
      S = zeros(4,5);
      A = zeros(4,5);
      v = 0;
      for j = 1:5
          A(:,j) = (Q^(j-1))*a;
          S(:,j) = (Q^(j-1))*s;
      end
      for q = 0:4
          assignin ('base',['U_' num2str(q)], Q^(q));
      end
      for h = 0:4
          helpvar = 0;
          for l = h+1:4
           for o = 1:4
               for p = 1:4
                   Hlp_h = evalin('base',['U_' num2str(h)]);
                   Hlp_l = evalin('base',['U_', num2str(l-h)]);
                   helpvar = helpvar + Hlp_h(i,o)*Hlp_l(o,p)*a(o)*a(p) - A(i,h+1)*A(i,l+1);
               end
           end
          end
          v = v + S(i,h+1) - (A(i,h+1))^2 + 2*(helpvar);
      end
end