\documentclass[12pt,a4paper]{article}

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\usepackage[T1]{fontenc}
\usepackage[utf8]{inputenc}
\usepackage{graphicx}
\usepackage{amsmath}
\usepackage{amssymb}
\usepackage{amsfonts}
\pagestyle{empty}

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\newcommand{\template}[5]
	{

\begin{flushleft}
			\begin{minipage}[t]{0.45\textwidth}
		Methods of Nonlinear Analysis in Differential and Integral Equations\\
		2021, May 15-16, May 22-23
		\end{minipage}
\end{flushleft}

	\vspace{1cm}
%	Title
\begin{center}
	{\Large \sc	\textbf{#1}}
\end{center}
%	Author
\begin{center}
	#2
\end{center}

%	Affiliation
\begin{center}
{\footnotesize 	#3}\\
{\footnotesize e-mail address: #4}
\end{center}

\begin{center}
\textbf{	Abstract}\\
\end{center}
	#5
}

\begin{document}

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	\template
	{
		% Title of presentation
		Enter the title of your lecture
	}
	{
		% Author 
		Author
	}
	{
		% Affiliation
		Department\\
		University\\
		Address\\
		City\\
		Country
	}
	{
		% e-mail address
		Enter email address
	}
	{
		% Abstract
		Enter abstract
	}

							% Optional

\begin{thebibliography}{00}
	\bibitem{}	% Author
				Author, 
			\emph
			{
				% Title of article
				Title of article,
			}
				% Journal
				Journal
\end{thebibliography}

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\end{document}