Dan wrote in [comment 11](https://forum.azimuthproject.org/discussion/comment/20339/#Comment_20339)

>\[
\Psi(x, y) =
\begin{cases}
\texttt{false} & \mbox{if } (x = 1 \mbox{ and } y \le 2) \mbox{ or } (x = 2 \mbox{ and } y \le 4) \\\\
\texttt{true} & \mbox{otherwise.}
\end{cases}
\]

Wouldn't we be able to buy one bread when y=2 and buy two bread when y=4?