\usepackage{xcolor}\usepackage{fontspec}\usepackage[sc]{mathpazo}\setmainfont[Ligatures=TeX]{Palatino Linotype}\usepackage{amssymb}\usepackage{amsmath}\usepackage{menukeys}\definecolor{darkblue}{rgb}{0,0,0.6}\usepackage[colorlinks=true,urlcolor=darkblue,linkcolor=darkblue]{hyperref}\newcommand{\dn}{\stackrel{\mbox{\scriptsize def}}{=}}%\definecolor{codegray}{gray}{0.9}\newcommand\grid[1]{%\begin{tikzpicture}[baseline=(char.base)] \path[use as bounding box] (0,0) rectangle (1em,1em); \draw[red!50, fill=red!20] (0,0) rectangle (1em,1em); \node[inner sep=1pt,anchor=base west] (char) at (0em,\gridraiseamount) {#1};\end{tikzpicture}}\newcommand\gridraiseamount{0.12em}\makeatletter\newcommand\Grid[1]{% \@tfor\z:=#1\do{\grid{\z}}}\makeatother \makeatletter\def\fnote{\gdef\@thefnmark{}\@footnotetext}\makeatother\newcommand{\HEADER}{{\bf Please submit your solutions via the email address 7ccsmsen\@gmail.com. Please submit only ASCII text or PDFs. Every solution should be preceeded by question. Solutions will only be accepted until 30th December!}\bigskip}