The MWE is
\documentclass[14pt]{beamer}% http://ctan.org/pkg/beamer
\let\Tiny\tiny% http://tex.stackexchange.com/q/58087/5764
\usetheme{Berkeley}
\makeatletter
\beamer@headheight=1.5\baselineskip
\makeatother
\setbeamercolor{normal text}{bg=black!10}
\begin{document}
\title[Title]{My title}
\subtitle{Subtitle}
\author{Author}
\institute[Institute]{My institute}
\date[Date]{My date}
\logo{\color{blue!50}\scalebox{2}{\TeX}} % you can % it
\begin{frame}
\titlepage
\end{frame}
\section{A section}
\subsection{A subsection}
\begin{frame}
\frametitle{Frame title}
\framesubtitle{frame subtitle}
\begin{center}
\begin{enumerate}
\item A1
\item A1
\begin{itemize}
\item A1
\item A1
\item A1
\end{itemize}
\end{enumerate}
\end{center}
\end{frame}
\end{document}
I want to put the text into the center as shown on the screenshot below. I tried using a center environment, but that didn't produce the expected output. Then I tried using vspace, but I need to adjust again and again. Is there any package I can use for this?

