$*$it says my Xm value is wrong... can someone help my MATLAB code$*$

write a script that generates a $1$D random walk for $N=20000$ markers. In the

beginning, the markers are randomly distributed in the interval $(-3,3).$ Generate

these initial positions and store them in $x0.$

Each step, the position $x$ of each marker should change by a randomly picked

number in the interval $(-1,1).$ All markers make $Nt=75$ steps. The result $(x-$

positions$)$ should be stored in an array called Xm$.$ Do NOT store the initial position

in Xm$.$ Your script should be vectorized.

IMPORTANT: the size of Xm should be Nt by N$.$

Script $o.$

$Nt=75$;

$N=20000$;

$x0=$rand$(1,N)**6-3$;

step$\_$changes $=$randi$([-1,1],Nt,N)$;

$xm=$ cumsum$($step$\_$changes, $1)+x0$;

size$(xm)$