For the following MATLAB code, what is the output result of $m-n?$

$A=\left[\begin{array}{cccccccccccccccccc}1& 2& 2& 3& 3& 1\text{;}& 0& 1& -1& 0& 2& -2\text{;}& 0& 0& 1& -2& 0& 3\end{array}\right]$

$b=\left[\begin{array}{ccc}1& 2& 0\end{array}\right]$;

$[m,n]=$size$([A$;$b])$;

$m-n$

an error message

$3$

$-3$

$4$

$-4$