	\tikzstyle{input_neuron}=[circle,draw=red!50,fill=red!10,thick,minimum size=6mm]
	\tikzstyle{hidden_neuron}=[circle,draw=blue!50,fill=cyan!10,thick,minimum size=5mm]
	\tikzstyle{output_neuron}=[circle,draw=green!50,fill=green!10,thick,minimum size=6mm]
	\tikzstyle{cpy_neuron}=[circle,draw=red!50,fill=red!50,thick,minimum size=6mm]
	\tikzstyle{input}=[circle,draw=black!50,fill=black!20,thick,minimum size=6mm]
	
\begin{center}
%\resizebox{}{}{

\begin{tikzpicture}[scale=0.75]

\node[hidden_neuron](A) {A};
\node[hidden_neuron,above=of A](B) {B};
\node[hidden_neuron,left=2cm of A ](C) {C};
\node[hidden_neuron,above = of C](D) {D};
\draw[thick,blue,->] (B) -- (A);
\draw[thick,blue,->] (D) -- (A);
\draw[thick,blue,->] (D) -- (C);
\draw[thick,blue,->] (B) -- (C);


\end{tikzpicture}
%}
\end{center}
