User:SamSim/TeXSandbox
\begin{array}{ll} x - \frac{1}{n} \lfloor nx \rfloor & \text{ if } \lfloor nx \rfloor \equiv 0 \bmod{2} \\
\frac{1}{n} \lfloor nx \rfloor - x + \frac{1}{n} & \text{ if } \lfloor nx \rfloor \equiv 1 \bmod{2}
\end{array}
\right.
\begin{array}{ll} x - \frac{1}{n} \lfloor nx \rfloor & \text{ if } \lfloor nx \rfloor \equiv 0 \bmod{2} \\
\frac{1}{n} \lfloor nx \rfloor - x + \frac{1}{n} & \text{ if } \lfloor nx \rfloor \equiv 1 \bmod{2}
\end{array}
\right.