[Tex/LaTex] How to remove text indent for the first paragraph only

formattingindentation

Almost all templates I tried have an indentation for all paragraphs. How do I remove the spaces before the first paragraph only?

\documentclass[12pt]{amsart}

\usepackage{amsfonts}
\usepackage{amsthm}
\usepackage{amsmath}
\usepackage{amscd}
\usepackage[latin2]{inputenc}
\usepackage{t1enc}
\usepackage[mathscr]{eucal}
\usepackage{indentfirst}
\usepackage{graphicx}
\usepackage{graphics}
\usepackage{pict2e}
\usepackage{epic}
\numberwithin{equation}{section}
\usepackage[margin=2.6cm]{geometry}
\usepackage{epstopdf} 

 \def\numset#1{{\\mathbb #1}}

\theoremstyle{plain}
\newtheorem{Th}{Theorem}[section]
\newtheorem{Lemma}[Th]{Lemma}
\newtheorem{Cor}[Th]{Corollary}
\newtheorem{Prop}[Th]{Proposition}

 \theoremstyle{definition}
\newtheorem{definition}{Definition}[section]
\newtheorem{Conj}[Th]{Conjecture}
\newtheorem{Rem}[Th]{Remark}
\newtheorem{?}[Th]{Problem}
\newtheorem{Ex}[Th]{Example}

\newcommand{\im}{\operatorname{im}}
\newcommand{\Hom}{{\rm{Hom}}}
\newcommand{\diam}{{\rm{diam}}}
\newcommand{\ovl}{\overline}
%\newcommand{\M}{\mathbb{M}}

\begin{document}

\title{example}
\begin{abstract}  a aaaaaaaaaaaaaa aaaaaa aaaaaa aaaaa aaaaaaa aaaaaaaaaaaa aaaaa aaaa aa aaaaaaaaaaaaaaaaaa aaaaaa aaaaa aaaaaaaaaaa aaaaaaaaaa aaaaa aaaaaaa aaaaaaaa aaaaaaaaaaaaaaaa
\end{abstract}

\maketitle 

\section{Prelim} 
I was often using any of the available “lorem ipsum” generators on the web while testing different things in LaTeX until I discovered that the Latex distribution provides packages generating blind text, which is definitely more convenient. With just a few lines of code, these packages will generate paragraphes, even whole documents with sections, paragraphs of text, lists, etc.

The first package that I will introduce is the “blindtext” package. First the language option as well as the package have to be loaded. Make sure you get the order right, otherwise your text might appear in latin by default.
\medskip

\section*{Reference}

\end{document}

Best Answer

(Creating community-wiki post to move answer out of comments.)

By default, LaTeX does not indent the first paragraph of sections, chapters, etc. This can be overriden by certain language-specific styles (with the babel package), or by loading the indentfirst package, as you have done here.

So if you don't want the first paragraph indented, don't load the indentfirst package: remove this line:

\usepackage{indentfirst}
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