\documentclass[12pt]{article}
\usepackage[utf8]{inputenc}
\usepackage[LGR,T1]{fontenc}
\usepackage[greek,english]{babel}
\usepackage{alphabeta}
\usepackage{amsmath}
\usepackage{amssymb}
\usepackage{amsthm}
\author{tolis}
\title{rand}
\begin{document}
\maketitle
\section{num1}
$
\left
\begin{array}{irc}
a & b & c \\
d & e & f 
\end{array}
\right
$
\end{document}
