\documentclass[10pt,a4paper]{article}

\usepackage[utf8]{inputenc}
\usepackage[T1]{fontenc}
\usepackage[english]{babel}
\usepackage{lmodern}
\usepackage[a4paper,margin=20mm,includeheadfoot,headheight=20pt,headsep=6mm,footskip=10mm]{geometry}
\usepackage{amsmath,amssymb}
\usepackage{graphicx}
\usepackage{xcolor}
\usepackage{fancyhdr}
\usepackage[hidelinks]{hyperref}

\setlength{\parindent}{0pt}
\setlength{\parskip}{3pt}

\newcommand{\StudentNames}{Student 1 (ID), Student 2 (ID), [Student 3 (ID)]}

\newif\ifmainreport
\mainreporttrue
\newcounter{MainReportPages}
\newcommand{\EndMainReport}{%
  \clearpage
  \setcounter{MainReportPages}{\numexpr\value{page}-1\relax}%
  \mainreportfalse
  \ifnum\value{MainReportPages}>4\relax
    \PackageWarningNoLine{elen0062-report}{MAIN REPORT EXCEEDS FOUR PAGES:
      \arabic{MainReportPages} counted pages. The AI-use
      declaration is excluded. Shorten the main report}%
  \fi
  {\small This page does not count toward the 4-page limit.\par}\medskip
}
\AtEndDocument{%
  \ifmainreport
    \PackageWarningNoLine{elen0062-report}{The required EndMainReport marker
      is missing. The main-report page count cannot be confirmed}%
  \fi
}

\pagestyle{fancy}
\fancyhf{}
\fancyhead[L]{%
  \ifmainreport
    \ifnum\value{page}>4\relax
      \Large\color{red!65!black}\textbf{MAIN REPORT EXCEEDS FOUR PAGES}%
    \else
      \small ELEN0062 -- Project 1%
    \fi
  \else
    \small ELEN0062 -- Project 1%
  \fi
}
\fancyhead[R]{%
  \ifmainreport
    \ifnum\value{page}>4\relax
    \else
      \small 2026--2027%
    \fi
  \else
    \small 2026--2027%
  \fi
}
\fancyfoot[R]{\ifmainreport\small\thepage\fi}
\renewcommand{\headrulewidth}{0.3pt}
\renewcommand{\footrulewidth}{0pt}

\begin{document}

\begin{center}
  {\large\bfseries Project 1 -- Classification algorithms}\par
  {\small\StudentNames}
\end{center}

\section{Decision tree}
\subsection{}

\subsection{}

\section{K-nearest neighbors}
\subsection{}

\subsection{}

\section{KDE Naive Bayes}
\subsection{}

\subsection{}

\subsection{}

\subsection{}

\section{Method comparison}
\subsection{}

\subsection{}

\subsection{}

\subsection{}

\subsection{}

% All report content must stay above this marker.
\EndMainReport

\section*{AI-use declaration}

\end{document}