function philp = optphi(cc,m,n)
global Ainf Binf
d = 1;
if size(Ainf,2)~=m^n
  Ainf = [];
end
if isempty(Ainf)
  Ainf = zeros(0,m^n);
  Binf = zeros(0,1);
  mn = repmat([m],[1 n]);
  rind = 0;
  for ind1 = 1:m^n
    for ind2 = ind1+1:m^n
      x = ind2coord(ind1,mn);
      y = ind2coord(ind2,mn);
      if length(find(x~=y))==1  % Hamming dist == 1
      for s = [-1,1]
        rind = rind+1;
        %if rind==131
        %  global x0 y0
        %  ind1,ind2,x,y
        %  x0=x,y0=y
        %  return
        %end
        Ainf(rind,ind1) =  s;
        Ainf(rind,ind2) = -s;
        Binf(rind,1) = d;
      end
      end
    end
  end
end
cc = cc(:);

%LB = zeros(size(cc))-1e-9;
%UB = LB + d*n + 1e-9;

[xp,fvalp] = linprog( cc,Ainf,Binf,[],[],[],[]);
[xn,fvaln] = linprog(-cc,Ainf,Binf,[],[],[],[]);
if abs(fvalp)>abs(fvaln)
  x = xp;
  fval = fvalp;
else
  x = xn;
  fval = fvaln;
end

philp = x(:)';
fvalp = abs(fval);

%[mval,y] = optmask(A0);
%if abs(fvalp-mval) > 1e-9
%  'not good'
%  keyboard
%end

return