\documentclass[UTF8,12pt]{article} % 12pt 为字号大小
\usepackage{amssymb,amsfonts,amsmath,amsthm,latexsym}
\usepackage{xeCJK}

\setCJKmainfont[BoldFont={SimHei},ItalicFont={KaiTi}]{SimSun}
\setCJKsansfont{SimHei}
\setCJKfamilyfont{zhsong}{SimSun}
\setCJKfamilyfont{zhhei}{SimHei}
\setCJKfamilyfont{zhkai}{KaiTi}
\setCJKfamilyfont{zhfs}{FangSong}
\setCJKfamilyfont{zhli}{LiSu}
\setCJKfamilyfont{zhyou}{YouYuan}

\newcommand*{\songti}{\CJKfamily{zhsong}} % 宋体
\newcommand*{\heiti}{\CJKfamily{zhhei}}   % 黑体
\newcommand*{\kaiti}{\CJKfamily{zhkai}}  % 楷体
\newcommand*{\fangsong}{\CJKfamily{zhfs}} % 仿宋
\newcommand*{\lishu}{\CJKfamily{zhli}}    % 隶书
\newcommand*{\yuanti}{\CJKfamily{zhyou}} % 圆体

%----------
% 版面设置
%----------
%首段缩进
\usepackage{indentfirst}
\setlength{\parindent}{2em}

%行距
\renewcommand{\baselinestretch}{1.4} % 1.4倍行距

%页边距
\usepackage[a4paper]{geometry}
\geometry{verbose,
    tmargin=1cm,% 上边距
    bmargin=1.5cm,% 下边距
    lmargin=1cm,% 左边距
    rmargin=1cm % 右边距
}


%----------
% 其他宏包
%----------
%图形相关
\usepackage[x11names]{xcolor} % must before tikz, x11names defines RoyalBlue3
\usepackage{graphicx}
\usepackage{pstricks,pst-plot,pst-eps}
\usepackage{subfig}
\def\pgfsysdriver{pgfsys-dvipdfmx.def} % put before tikz
\usepackage{tikz}

%原文照排
\usepackage{verbatim}

%网址
\usepackage{url}

%----------
% 习题与解答环境
%----------
%习题环境
\theoremstyle{definition} 
\newtheorem{exs}{习题}
\newtheorem{lemma}{引理}

%解答环境
\ifx\proof\undefined\
\newenvironment{proof}[1][\protect\proofname]{\par
    \normalfont\topsep6\p@\@plus6\p@\relax
    \trivlist
    \itemindent\parindent
    \item[\hskip\labelsep
    \scshape
    #1]\ignorespaces
}{%
    \endtrivlist\@endpefalse
}
\fi

\renewcommand{\proofname}{\it{证明}}
\newcommand{\ve}{\mathbf}
\newcommand{\Ve}{\overrightarrow}
\newcommand{\V}{\boldsymbol}
\DeclareMathOperator{\Span}{Span}
\DeclareMathOperator{\Null}{Null}
\DeclareMathOperator{\crk}{colrank}
\DeclareMathOperator{\rrk}{rowrank}
\DeclareMathOperator{\col}{Col}
\DeclareMathOperator{\row}{Row}
\DeclareMathOperator{\rk}{rank}
\DeclareMathOperator{\im}{Im}
\DeclareMathOperator{\kr}{Ker}
\DeclareMathOperator{\nl}{null}

\makeatletter
% overline
\newcommand{\dbloverline}[1]{\overline{\dbl@overline{#1}}}
\newcommand{\dbl@overline}[1]{\mathpalette\dbl@@overline{#1}}
\newcommand{\dbl@@overline}[2]{%
    \begingroup
    \sbox\z@{$\m@th#1\overline{#2}$}%
    \ht\z@=\dimexpr\ht\z@-2\dbl@adjust{#1}\relax
    \box\z@
    \ifx#1\scriptstyle\kern-\scriptspace\else
    \ifx#1\scriptscriptstyle\kern-\scriptspace\fi\fi
    \endgroup
}
% underline
\newcommand{\dblunderline}[1]{\@@underline{\dbl@underline{#1}}}
\newcommand{\dbl@underline}[1]{\mathpalette\dbl@@underline{#1}}
\newcommand{\dbl@@underline}[2]{%
    \begingroup
    \sbox\z@{$\m@th#1\@@underline{#2}$}%
    \dp\z@=\dimexpr\dp\z@-2\dbl@adjust{#1}\relax
    \box\z@
    \ifx#1\scriptstyle\kern-\scriptspace\else
    \ifx#1\scriptscriptstyle\kern-\scriptspace\fi\fi
    \endgroup
}
\newcommand{\dbl@adjust}[1]{%
    \fontdimen8
    \ifx#1\displaystyle\textfont\else
    \ifx#1\textstyle\textfont\else
    \ifx#1\scriptstyle\scriptfont\else
    \scriptscriptfont\fi\fi\fi 3
}
\newcommand{\pr}{\prime}
\newcommand{\va}{\V{\alpha}}
\newcommand{\vb}{\V{\beta}}
\newcommand{\B}{\mathcal{B}}
\makeatother
\begin{document}
    \title{\vspace{-2cm}}
    \author{}
    \date{\today}
    \maketitle{}
\end{document}