\usepackage{natbib}
\usepackage{graphicx}
\usepackage{tikz}
\usepackage{amsmath}
\usepackage{amsfonts} 
\usepackage{mathtools}
\usepackage[edges]{forest}

\[ 
    \begin{forest}
    for tree={
        grow=south,
        circle, draw, minimum size=3ex, inner sep=1pt,
        s sep=7mm
            }
    [$\neg$ 
        [ $\rightarrow$
            [$\neg$
                [ $\rightarrow$
                    [$\vee$
                        [$r$]
                        [$p$]
                    ]
                    [$q$]
                ]
            ]
            [ $\wedge$
                [$q$]
                [$p$]
            ]
        ]
    ]
    \end{forest}
\]
