\documentclass[10pt]{article}

% mathpartir.sty can be found here: http://pauillac.inria.fr/~remy/latex/mathpartir.sty
\usepackage{mathpartir}  % This package is required for the inferrule command.  
\usepackage[letterpaper, landscape, margin=1in]{geometry}

\begin{document}
\begin{center}
{\bf Assignment 2: Loops and Proofs \\15-424/15-624 Foundations of Cyber-Physical Systems  }\\
\end{center}

% Use \\ to separate branches in your proof (for example in non-deterministic choice). 
	\begin{mathpar}
	\inferrule*
		[left={\it label}]
		{top1 \\ top2}
		{bot}
	\end{mathpar}

% Here is how your proof should start.  Finish it from bottom to top. 
	\begin{mathpar}
	\inferrule*
		[left={\it ind'}]
		{\inferrule*[left=?]{TOP}{BOTTOM} \\ \inferrule*[left=?]{TOP}{BOTTOM}\\ \inferrule*[left=?]{TOP}{BOTTOM}
		}
		{x \geq 0 \wedge a > 0 \wedge A > 0 \wedge v \geq 0 \vdash [((a := 0 \cup a:=A); x' = v, v' = a)^*]x\geq 0}
	\end{mathpar}	
	


\end{document}
