代码小题部分出现了啥问题？

\documentclass[a4paper]{article}

\renewcommand{\baselinestretch}{1.5}
\topmargin -30mm \oddsidemargin 0mm \evensidemargin 0mm \textwidth 180mm \textheight 237mm
\addtolength{\headsep}{13mm}

\newif\ifpdf
\ifx\pdfoutput\undefined
\pdffalse
\else
\pdfoutput=1
\pdftrue
\fi

\ifpdf
\usepackage[pdftex]{graphicx}
\pdfcompresslevel=9
\else
\usepackage[dvips]{graphicx}
\fi

\ifpdf
\DeclareGraphicsExtensions{.jpg,.pdf,.mps,.png}
\fi

\usepackage{fancyhdr}
\usepackage{afterpage}
\usepackage{lastpage}
\usepackage{listings}
\usepackage{CJK,CJKnumb}
\usepackage{indentfirst}
\usepackage{esint}

\begin{document}

\begin{CJK*}{GBK}{song}
\CJKtilde \CJKindent

\newcounter{mynum}
\newcounter{subnum}[mynum]
\newcommand{\dati}{\stepcounter{mynum}\CJKnumber{\arabic{mynum}}、\ }
\newcommand{\xiaoti}{\stepcounter{subnum}\arabic{subnum}.\ }
\newcommand{\kg}[1]{\,\underline{\hspace{#1em}}\,}

\newsavebox{\firstpgframe}
\sbox{\firstpgframe}{\parbox{157mm}{
\begin{center}
\begin{minipage}[t][153mm][t]{157mm}
\makebox[4mm][l]{\fbox{\parbox[t][153mm][t]{157mm}{\ }}}
\end{minipage}
\end{center}
}}

\pagestyle{fancy}

\renewcommand{\headrulewidth}{0pt}

\newsavebox{\otherpgframe}
\sbox{\otherpgframe}{\parbox{157mm}{
\begin{center}
\begin{minipage}[t][224mm][t]{157mm}
\makebox[4mm][l]{\fbox{\parbox[t][226mm][t]{157mm}{\ }}}
\end{minipage}
\end{center}
}}

\vspace{4mm}
\large
\CJKindent
\newenvironment{mytext}
{\begin{list}{}{%
\setlength{\leftmargin}{15mm}
\setlength{\rightmargin}{12mm}
}\item[]}{\end{list}}

\begin{mytext}

\xiaoti 等式：$\overline{\text{南京}54}=39\times \overline{1\text{市}6}$南京市恰好出现1、2、3、4、$\cdots$、9九个数字，“南京市”代表的三位数是\underline{\makebox[34mm][c]{}}。

\end{mytext}

\clearpage
\end{CJK*}
\end{document}