I dno't know how to draw arrows as the above figure, and the code I wrote for the four points don't even show up on a result. Why my points don't appear? And what should be added for the arrows?
\documentclass{article}
\usepackage{tikz}
\begin{document}
\begin{tikzpicture}
\draw [fill=black](0, 0) circle;
\draw [fill=black](1, 0) circle;
\draw [fill=black](1, -1) circle;
\draw [fill=black](0, -1) circle;
\end{document}
\documentclass{article}
\usepackage{tikz}
\begin{document}
\begin{tikzpicture}
\end{document}
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