begin{figure}[H] centering
    includegraphics[width=0.48textwidth, keepaspectratio]{figure/s0}
    hspace{2mm}
    includegraphics[width=0.48textwidth, keepaspectratio]{figure/s1}
    hfill
    includegraphics[width=0.48textwidth, keepaspectratio]{figure/s2}
    hspace{2mm}
    includegraphics[width=0.48textwidth, keepaspectratio]{figure/s3}
    hfill
end{figure}