\documentclass{scrartcl}
\usepackage{amssymb, amsmath} % needed for math
\usepackage[utf8]{inputenc} % this is needed for umlauts
\usepackage[ngerman]{babel} % this is needed for umlauts
\usepackage[T1]{fontenc}    % this is needed for correct output of umlauts in pdf
\usepackage[margin=2.5cm]{geometry} %layout
\usepackage{hyperref}   % links im text
\usepackage{parskip}
\usepackage{multicol}

\title{Minimal distance to a cubic function}
\author{Martin Thoma}

\hypersetup{ 
  pdfauthor   = {Martin Thoma}, 
  pdfkeywords = {}, 
  pdftitle    = {} 
} 

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\begin{document}
\section{mathcal}
\begin{multicols}{3}
\begin{itemize}
    \item $\mathcal{A}$
    \item $\mathcal{B}$
    \item $\mathcal{C}$
    \item $\mathcal{D}$
    \item $\mathcal{E}$
    \item $\mathcal{F}$
    \item $\mathcal{G}$
    \item $\mathcal{H}$
    \item $\mathcal{I}$
    \item $\mathcal{J}$
    \item $\mathcal{K}$
    \item $\mathcal{L}$
    \item $\mathcal{M}$
    \item $\mathcal{N}$
    \item $\mathcal{O}$
    \item $\mathcal{P}$
    \item $\mathcal{Q}$
    \item $\mathcal{R}$
    \item $\mathcal{S}$
    \item $\mathcal{T}$
    \item $\mathcal{U}$
    \item $\mathcal{V}$
    \item $\mathcal{W}$
    \item $\mathcal{X}$
    \item $\mathcal{Y}$
    \item $\mathcal{Z}$
\end{itemize}
\end{multicols}
\end{document}