function H = getH(A,i0)
if ~exist('i0','var')
  i0 = 1;
end
[n,n,T] = size(A);
hh = zeros(T,1);
for t=1:T
  h = 0;
  for i=1:n
    for j=i+1:n
      x = A(:,i,t);
      y = A(:,j,t);
      d = .5*sum(abs(x-y));
      if d>h
        h=d;
      end
    end
  end
  hh(t) = h;
end
H = 1;
for i=i0:T
  x = 1;
  for j=i0:i
    x = x * hh(j);
  end
  H = H+x;
end
return