I’m having these errors: Undefined control sequence (with the BlankLine),Missing $ in all the raws I use it and also a Missing } inserted Missing { inserted in the List1 and List2 line.

begin{algorithm}[b]
caption{Find aa}
BlankLine
$a$ leftarrow input ;
newline
$List1$ leftarrow x$_$x$_$x$_$x(a,a)
newline
$List2$ leftarrow x$_$x$_$x$_$x(a,List1,List2)
newline
$H$ leftarrow a(a,a,a,a)
newline
newline
newline
Return $x$;
end{algorithm}

These are the packages I have used

usepackage{moreverb}
usepackage{graphicx}
usepackage{ifthen}
usepackage{amsmath,amsfonts}
usepackage{algorithm}
usepackage{algorithmic}