Converting Four Variable OR to NOR (using only NOR GATE)

Question

I want to convert a four variable OR (i.e. OR(A,B,C,D)) to NOR. I did this using 6 two variable NOR like the picture below. but I think it can be done easier. Can anyone suggest any way to do this and avoid using this amount of gates. For example using a 4 variable NOR instead of this 2 variable NORs.

Actually I did this:

$OR(A,B,C,D) = OR(OR (A,B) , OR(C,D)) = NOT(NOR(NOT(NOR(A,B)) , NOT(NOR(C,D)))$

Answer 1

Apply $Q=\overline{\overline{Q} \vee \overline{Q}}.$
In the present case, with the use of two $4-$inputs NORs and one $2-$inputs NOR you have $$A\vee B\vee C \vee D = \overline{\overline {A\vee B\vee C \vee D}\vee \overline{A\vee B\vee C \vee D}}$$