Context Sensitive Grammar for the language ${a^nb^nc^nmid n≥1}$

I tried many grammars and so far I got this one:

begin{align}
&S to aSXY mid abc \
&YX to XY \
&aX to ab \
&bX to bb \
&bY to bc \
&cY to cc
end{align}

Is my grammar correct? Is there a simpler one?