# beamer and ams symbols

I would like to use some ams symbol in my presentation, like arrows or aother kind of symbol. When I use the command \ding with the relative code for display the symbol, I receive an error during the compile procedure:

! Undefined control sequence.
\beamer@doifinframe ...ne & n. \\ \midrule A\ding
{221}B\ding {221}C\ding {2...
l.40 \end{frame}
The control sequence at the end of the top line
of your error message was never \def'ed


My code is:

\documentclass[xcolor=table, t]{beamer}

\usepackage{booktabs}
\usepackage{tikz}
\usepackage{amsmath}
\usepackage{amsfonts}
\usepackage{amssymb}

\title{my presentation}
\author{name}

\begin{document}

\begin{frame}
\maketitle
\end{frame}

\begin{frame}
\frametitle{title}

\begin{table}[]%\footnotesize
\centering
\medskip
\begin{tabular}{lr}
\toprule
Transizione & n. \\
\midrule
A\ding{221}B\ding{221}C\ding{221}A & 54 \\
D\ding{221}C\ding{221}B\ding{221}C\ding{221}D & 30 \\
D\ding{221}C\ding{221}B\ding{221}C & 23 \\
\bottomrule
\end{tabular}
\end{table}
\end{frame}

\end{document}


thanks in advance for the help

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\usepackage{pifont}