Being a mechanical engineer I never had the necessity to draw chemical formulas/molecule structures in LaTeX, but now I have to draw the structure of Polyethylene glycol. So I was looking at examples of how to use chemfig and doing the chain was pretty basic, but I have no idea how to put the parentheses around the bit to be repeated n times. Could someone please help me out? Thanks!
MWE
\documentclass{scrreprt}
\usepackage{chemfig}
\begin{document}
\chemfig{H-[:30]O-[:-30]-[:30]-[:-30]O-[:30]H}
\end{document}
I got:
I need:


