\item \ifassignmentsheet \points{2}
  \dpllDescriptionAssignmentSheet
\else \prac
  \dpllDescription{negative}
\fi

\begin{dpllCNFInput}
        \item $\{a, \lnot b, c\}$
        \item $\{b, \lnot c, d\}$
        \item $\{a, \lnot b\}$
        \item $\{a, c\}$
        \item $\{\lnot c, \lnot d\}$
\end{dpllCNFInput}