\documentclass[]{}
% use this to comment out a line


\documentclass[16pt]{article}
\documentclass[12pt, a4paper]{report}

\usepackage[]{}

\usepackage{xeCJK}
\setCJKmainfont[BoldFont={* Bold}]{Noto Sans CJK TC}
\setCJKsansfont[]{Noto Sans CJK TC}

\usepackage[margin=2cm]{geometry}

\newcommand{\hello}{Hello, world!}
\newcommand{\friendStatement}[2]{#1 is a friend of #2's}

\hello
\friendStatement{Nobody}{Brine}

\newcounter{cnt}
\setcounter{cnt}{10}
\stepcounter{cnt}
\addtocounter{cnt}{5}
\setcounter{cnt}{\value{cnt2}}

int cnt = 0;
cnt = 10;
cnt++;
cnt += 5;
cnt = cnt2;

\title{Never gonna give you up}
\author{Rick Astley}
\date{July 1987}

\begin{document}
\maketitle

\section{Never gonna let you down}
\subsection{stuff}

Make sure to leave an empty line.

If you want two seperate sentences.

\end{document}

\begin{document}
    \begin{titlepage}
        \begin{center}
            \huge TITLE\\
            \vspace{3.14cm}
            \large SUBTITLE
            \vfill
            \small end of page.
        \end{center}
    \end{titlepage}
\end{document}

\usepackage{graphicx}

\includegraphics[width=5cm]{PATH}

\usepackage{enumerate}

\begin{document}
    \begin{enumerate}[I]
    	\item one
    	\item two
    \end{enumerate}
\end{document}

\begin{figure}
    \centering
    \includegraphics{pen.png}
    \caption{this is a pen}
    \label{fig:pic1}
\end{figure}

\pageref{fig:pic1}

\begin{table}[]
\begin{tabular}{|c|r|r|}
\hline
名字    & \multicolumn{1}{c|}{原始} & \multicolumn{1}{c|}{調分後} \\ \hline
平均    & 52                      & 72                       \\ \hline
Brine & 48                      & 68                       \\ \hline
您     & 100                     & 120                      \\ \hline
\end{tabular}
\end{table}

$a^2 + b^2 = c^2$

\[
e^{ix} = \cos x + \sin x
\]

\Alpha \alpha
\Beta \beta

\frac{xy}{x + y}
y_{hello}
x^{\log_2 n}
\sqrt{-1}
\sqrt[3]{8}
\lceil x \rceil
\lfloor x \rfloor

\frac{xy}{x + y}
y_{hello}
x^{\log_2 n}
\sqrt{-1}
\sqrt[3]{8}
\lceil x \rceil
\lfloor x \rfloor

O(n^2 + q \sqrt n) \mathcal O(n^2 + q \sqrt n)
log x + log y = log xy \log x + \log y = \log xy
sin^2 x + cos^2 x = 1 \sin^2 x + \cos^2 x = 1

\displaystyle \sum_{n = 1}^{5} n^2
\displaystyle \prod_{n = 1}^{5} n
\displaystyle \frac{\partial}{\partial x} x^2 y
\displaystyle \int_{1}^{5} e^x dx

\pm, \mp
\div
\vec a \cdot \vec b
\vec a \times \vec b
69^{\circ}\text C

\tiny = smallest
\scriptsize = very small
\footnotesize = smaller
\small = small
\normalsize = normal
\large = large
\Large = Large
\LARGE = LARGE
\huge = huge
\Huge = Huge

#include <iostream>

using namespace std;

int main() {
    cout << "Hello, world\n";
}