\tikzstyle{hidden_neuron}=[circle,draw=red!50,fill=orange!10,thick,minimum size=.2mm]
\tikzstyle{input_neuron}=[circle,draw=blue!50,fill=blue!10,thick,minimum size=1mm]
\tikzstyle{output_neuron}=[circle,draw=green!50,fill=green!20,thick,minimum size=1mm]
\tikzstyle{input}=[circle,draw=black!50,fill=black!20,thick,minimum size=.2mm]
%\vspace{0.8in}
\begin{center}

\begin{tikzpicture}

	%	 layer 1
%	\node [neuron_type] (var_name) at (X,Y)  {$Text$} ;
	\node [input_neuron] (ain1) at (4,4)  {$D$} ;
	\node [input_neuron] (ain2) at (6,4)  {$I$} ;
	
	%	layer2
%	\node [input_neuron] (in3) at (4,3)  {$C$} ;
	\node [input_neuron] (ain4) at (5,2.5)  {$G$};
	\node [input_neuron] (ain5) at (7,2.5)  {$S$} ;
	
%	%	layer3
	\node [input_neuron] (ain6) at (5,0.75)  {$L$} ;
	
	\draw [->, line width=0.5mm] (ain1) -- (ain4);
	\draw [->, line width=0.5mm] (ain2) -- (ain4);
	\draw [->, line width=0.5mm] (ain2) -- (ain5);
	\draw [->, line width=0.5mm] (ain4) -- (ain6);

\end{tikzpicture}
\end{center}