Equation with cases

[seghier]

Hello
How to create this equation?

\documentclass{article}
\usepackage{amssymb}
\usepackage[overload]{empheq}
\newcommand{\for}{\text{for }}

\begin{document}

\begin{equation*}[right=\empheqrbrace{=xy.}]
    X(m,n)=
    \begin{cases}
      x(n),& \for 0\leqslant n \leqslant 1 \\
      x(n-1),& \for 0\leqslant n \leqslant 1 \\
      x(n-1),& \for 0\leqslant n \leqslant 1
    \end{cases}
\end{equation*}

\end{document}