\ncarc[arcangle=0]{int}{null}\ncput*[npos=.50]{aktop = '\textbackslash 0'}
\ncarc[arcangle=0]{null}{calc}
-\ncarc[arcangle=0]{calc}{read}\ncput*[npos=.50]{int\_done$\uparrow$}
+\ncarc[arcangle=0]{calc}{read}\ncput*[npos=.45]{else}
\ncarc[arcangle=0]{calc}{done}\ncput*[npos=.50]{aktop = DONE}
\end{document}