% Fichier ex4.8.3.tex - Ch. Rolland/O Reilly France
\documentclass{article}
\usepackage[latin1]{inputenc}
\usepackage{amsmath}
\begin{document}
\begin{align}
u & \equiv v + 1 \pmod{n^2} \\
u & \equiv v + 1 \mod{n^2} \\
u & \equiv v + 1 \pod{n^2} 
\end{align}
\end{document}
