\documentclass{article}

\usepackage[utf8]{inputenc} % this is needed for umlauts
\usepackage[ngerman]{babel} % this is needed for umlauts
\usepackage[T1]{fontenc}    % this is needed for correct output of umlauts in pdf

\usepackage[pdftex,active,tightpage]{preview}
\setlength\PreviewBorder{2mm}
\usepackage{tikz}
\usetikzlibrary{shapes, calc, decorations, automata}
\usepackage{amsmath,amssymb}

\tikzstyle{midnode}=[
    draw=blue!70,   % draw the border with 70% transparent blue
    rectangle,      % the shape of the node is a rectangle
    fill=blue!10,   % fill the box with 20% blue
    text width=1cm,
    text centered]

\tikzstyle{smallnode}=[
    draw=blue!70,   % draw the border with 70% transparent blue
    rectangle,      % the shape of the node is a rectangle
    fill=blue!10,   % fill the box with 20% blue
    text width=0.4cm,
    text centered]

\begin{document}
\begin{preview}
\begin{tikzpicture}[->,>=stealth,auto, very thick, scale=5]
        % Draw the vertices.
        \node[midnode] (s) {Start};
        \node[smallnode, right of=s, node distance=1.8cm] (a) {1};
        \node[smallnode, below of=a] (b) {2};
        \node[smallnode, right of=a, node distance=1.8cm] (c) {3};
        \node[smallnode, below of=c] (d) {4};
        \node[smallnode, right of=c, node distance=1.8cm] (e) {5};
        \node[midnode, below of=e] (x) {Stopp};

        % Connect vertices with edges
        \path (s) edge node {} (a);
        \path (a) edge node {} (c);
        \path (a) edge node {} (b);
        \path (b) edge node {} (c);
        \path (c) edge node {} (d);
        \path (c) edge node {} (e);
        \path (d) edge node {} (e);
        \path (e) edge node {} (x);

\end{tikzpicture}
\end{preview}
\end{document}