# Missing \endcsname inserted with beamer document

I have created a beamer presentation in Overleaf but I don't know what my error means

>Missing \endcsname inserted.
\relax
l.99 \end{frame}


This is my tex

\documentclass{beamer}
\usetheme{Warsaw}
\title{Gettysburg Cemetery Dedication}
\author{Abraham Lincoln}
\institute{United States of America}
\date{19 Nov 1863}

\begin{document}
\begin{frame}
\titlepage % beamer’s \maketitle
\end{frame}

\begin{frame}
\frametitle{Outline}
\begin{itemize}
\item Agenda
\item Review
\item Summary
\end{itemize}
\end{frame}
\tableofcontents

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
\section{Agenda}

\begin{frame}
\frametitle{Agenda}
\begin{itemize}
\item Met on battlefield (great)
\item Dedicate portion of field --- fitting!
\end{itemize}
\end{frame}

\begin{frame}
\frametitle{Not on Agenda!}
\begin{itemize}
\item Dedicate
\pause\item Consecrate
\pause\item Hallow (in narrow sense)
\pause\item Note or remember what we say
\end{itemize}
\end{frame}
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
\section{Review}
\begin{frame}
\frametitle{Key Objectives \& Success Factors}
\begin{itemize}
\item What makes nation unique:
\begin{itemize}
\item Conceived in Liberty
\item are equal
\end{itemize}

\begin{block}{Shared vision:}
\begin{itemize}
\item  New birth of freedom.
\item  Gov't of/for/by the people.
\end{itemize}
\end{block}

\end{itemize}
\end{frame}

\begin{frame}
\frametitle{Organizational Overview}
\begin{figure}
\includegraphics[width=0.5\textwidth]{gettysburg_graph}
\end{figure}
%$$%\lable{Four Score and Seven} %-(4 * 20 + 7) = -87 %$$
\end{frame}

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
\section{Summary}
\begin{frame}
\frametitle{Summary}
\begin{columns}
\begin{column}
\begin{itemize}
\item New nation
\item Civil war
\item Dedicate field
\end{itemize}
\end{column}

\begin{column}
\begin{itemize}
\item Dedicated to unfinished work
\item New birth of freedom
\item Government not perish
\end{itemize}
\end{column}
\end{columns}
\end{frame}
\end{document}

• Welcome to TeX.SX! I believe that the width argument to \begin{column} is mandatory: so something like \begin{column}{0.4\linewidth} should be used. – egreg Oct 10 '15 at 15:02
• Welcome to TeX.SX! You've identified your problem clearly here, but your example is much too long; please look into how to create a minimal working example (meta.tex.stackexchange.com/questions/228/…), which will make it much easier for people to isolate your problem and help you solve it. More often than not, it will help you solve it yourself, as well. – dgoodmaniii Oct 10 '15 at 15:07

There are two mistakes in your code:

1. You have \lable instead of \label in an equation (it's commented out in your code but once you uncomment it you'll get an error).
2. The column environment requires a length specifying the width.

The corrected code (I marked the changes using %HERE):

\documentclass{beamer}
\usetheme{Warsaw}

\begin{document}

\begin{frame}
\frametitle{Organizational Overview}
\begin{figure}
\includegraphics[width=0.5\textwidth]{example-image-a}
\end{figure}
%$$%\label{Four Score and Seven}% HERE %-(4 * 20 + 7) = -87 %$$
\end{frame}

\section{Summary}
\begin{frame}
\frametitle{Summary}
\begin{columns}
\begin{column}{.5\linewidth}% HERE
\begin{itemize}
\item New nation
\item Civil war
\item Dedicate field
\end{itemize}
\end{column}

\begin{column}{.5\linewidth}% HERE
\begin{itemize}
\item Dedicated to unfinished work
\item New birth of freedom
\item Government not perish
\end{itemize}
\end{column}
\end{columns}
\end{frame}

\end{document}