\tikzstyle{hidden_neuron}=[circle,draw=red!50,fill=orange!10,thick,minimum size=.2mm]
\tikzstyle{input_neuron}=[circle,draw=blue!70,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 [input_neuron] (in1) at (5,4)  {$D$} ;
	\node [input_neuron] (in2) at (7,4)  {$I$} ;
	
%	layer2
	\node [input_neuron] (in3) at (4,2.5)  {$C$} ;
	\node [input_neuron] (in4) at (6,2.5)  {$G$};
	\node [input_neuron] (in5) at (8,2.5)  {$S$} ;
	
%	layer3
	\node [input_neuron] (in6) at (6,1)  {$L$} ;
	
	
	\draw [->, line width=1mm] (in1) -- (in4);
	\draw [->, line width=1mm] (in2) -- (in4);
	\draw [->, line width=1mm] (in2) -- (in5);
	\draw [->] (in5) -- (in6);
	\draw [->] (in3) -- (in6);
	\draw [->, line width=1mm] (in4) -- (in6);
	
	
\end{tikzpicture}
\end{center}