你好，我运行时出现 tex 文件错误

Question

当我运行 tex 文件 bt Winedit 时，输出如下 Latex 错误 File beamer.cls not found

\documentclass[10pt]{beamer}
\usetheme{Warsaw}
\usepackage{times}
\usepackage[T2A]{fontenc}
\usepackage[english, russian]{babel}
\usepackage{pgf,pgfarrows,pgfnodes,pgfautomata,pgfheaps}
\usepackage{amssymb, amsfonts, amsthm, amsmath}
\usepackage[cp1251]{inputenc}

    \usepackage{ragged2e}
    \usefonttheme{professionalfonts}
 \renewcommand{\baselinestretch}{1.04}
\sloppy \setlength{\parindent}{.4in}
\renewcommand{\raggedright}{\leftskip=0pt \rightskip=0pt plus 0cm}
\setbeamercolor{bluetext_color}{fg=blue}
\newcommand{\bluetext}[1]{{\usebeamercolor[fg]{bluetext_color}#1}}

\newcommand{\toright}{\hskip25mm}
\title{Mathematics}


\begin{document}
\fontsize{10}{14}\selectfont
\frame{\titlepage}
\def\ibb{\int\limits_{-\infty}^{+\infty}}
\def\iob{\int\limits_0^{\infty}}
\def\ikb{\int\limits_{x_0}^{\infty}}
\def\iab{\int\limits_{a}^{b}}
\def\ibx{\int\limits_{-\infty}^x}
\def\ibo{\int\limits_{-\infty}^0}
\def\iobx{\int\limits_0^{x_0}}
\def\ixbb{\int\limits_{-x_0}^{\infty}}
\def\l{\left(}
\def\r{\right)}
\def\q{\left[}
\def\m{\right]}
\def\dis{\displaystyle}
\setbeamercolor{bluetext_color}{fg=blue}
\setlength{\parindent}{.4in}
\renewcommand{\raggedright}{\leftskip=0pt \rightskip=0pt plus 0cm}
\begin{frame}\justifying\frametitle{Section1 }

$$\left\{
    \begin{array}{ll}
      (a\varphi^3(x)+(1-a)\varphi(x))\psi^3(x)=\ibb K(x-t)\varphi(t)dt,\quad x\in\mathbb{R}\qquad\qquad\qquad\qquad\qquad\,(1)  \\
      \lim\limits_{x\rightarrow\pm\infty}\varphi(x)=\pm1\,\,\,\,\,\qquad\qquad\qquad\qquad\qquad\qquad\qquad\qquad\qquad\qquad\qquad\qquad\qquad\quad\,\,\,\,\,(2)
    \end{array}
  \right.
$$

\setcounter{equation}{2}
\begin{equation}\label{3}
K(-x)=K(x),\quad x\in \mathbb{R}^+\equiv[0;+\infty),\quad K(\tau)>0,\quad \tau\in\mathbb{R},
\end{equation}
\begin{equation}\label{4}
K\in L_{\infty}(\mathbb{R})\cap L_1(\mathbb{R}),\quad K(x)\downarrow \,\mbox{ïî}\,\, x \,\,\mbox{íà}\,\,\mathbb{R}^+,
\end{equation}
\end{frame}
\end{document}