\begin{scope}[node distance=0.75cm]

\node (DoDo4) [inner xsep=0.01cm, inner ysep=0.03cm] at (0, 0) {@};

\node (TimesAp)
  [xshift=0.25cm, inner xsep=0.01cm, inner ysep=0.03cm, below of=DoDo4, left of=DoDo4]
  {@};

\node (Times)
  [xshift=0.25cm, inner xsep=0.01cm, inner ysep=0.03cm, below of=TimesAp, left of=TimesAp]
  {$+$};

\node (Times44) 
  [xshift=-0.5cm, inner xsep=0.01cm, inner ysep=0.03cm, below of=DoDo4, right of=DoDo4, yshift=-0.5cm, color=blue]
  {@};

\node (4)
  [xshift=-0.25cm, inner xsep=0.01cm, inner ysep=0.03cm, below of=Times44, right of=Times44, yshift=-0.75cm, color=blue]
  {4};

\node (Times4)
  [xshift=0.25cm, inner xsep=0.04cm, inner ysep=0.05cm, below of=Times44, left of=Times44, xshift=2, color=blue]
  {@};

\node (Times2)
  [xshift=0.25cm, inner xsep=0.01cm, inner ysep=0.03cm, below of=Times4, left of=Times4, color=blue]
  {$+$};

\draw[->] (DoDo4)   to (TimesAp);
\draw[->] (TimesAp) to (Times);
\draw[->] (TimesAp) to (Times44);
\draw[->] (DoDo4)   to (Times44);
\draw[->,color=blue,dashed] (Times44) to (Times4);
\draw[->,color=blue,dashed] (Times4)  to (Times2);
\draw[->,color=blue,dashed] (Times4)  |- (4);
\draw[->,color=blue,dashed] (Times44) to (4);

\end{scope}