[xx yy]=meshgrid(mN, mN);
L1= union(L1, L2, 'rows');
plot(S(:, 1),S(:,2) ,'o','color', 'b', 'markersize',4, 'linewidt',1);
[mx_mat, my_mat] = ndgrid(-(MAX_x - MIN_x):(MAX_x - MIN_x), -(MAX_y - MIN_y):(MAX_y - MIN_y));
mx_vec = mx_mat(:); my_vec = my_mat(:);
index = (mx_vec == S(ii, 1) - S(jj, 1) & my_vec == S(ii, 2) - S(jj, 2));
w( index ) = w( index ) + 1;
n1{ index } = [n1{ index }; S(ii, :)];
n2{ index } = [n2{ index }; S(jj, :)];
SS = repmat(S, [LEN_S, 1]);
SS_= kron(S, ones(LEN_S, 1));
[D1, ~, ind_SS] = unique(SS - SS_, 'rows', 'sorted');
plot(D1(:,1), D1(:,2) ,'square','color', 'r', 'markersize',5, 'linewidt',2);hold on
plot(D1(:,1), D1(:,2) ,'square','color', 'b', 'markersize',5, 'linewidt',2);hold on
axis([-inf inf -inf inf ]);