\documentclass{article}
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\title{Derevyannykh.2}
\author{Mikhail Derevyannykh }
\date{July 2018}

\begin{document}

\maketitle


\section{Task3}

\begin{tabular}{l c c c c}
    \toprule
    \multirow{2}{*}{
    \begin{tabular}{c}
         \quad \\
         \quad \\
         \rule{0}{4.0mm}
         \textbf{Characteristic}
    \end{tabular}
    }

    & \multicolumn{2}{c}{\textbf{12-17 years of age}} & \multicolumn{2}{c}{\textbf{18-25 years of age}} \\ \cline{2-5}
    &
    \begin{tabular}{c}
         \rule{0}{4.0mm}
         Intermittent^a  \\
         \% (95\% CI)
    \end{tabular}

    &
    \begin{tabular}{c}
        \rule{0}{4.0mm}
         Daily^b  \\
         \% (95\% CI)
    \end{tabular}

    &
    \begin{tabular}{c}
        \rule{0}{4.0mm}
         Intermittent^a  \\
         \% (95\% CI)
    \end{tabular}

    &
    \begin{tabular}{c}
        \rule{0}{4.0mm}
         Daily^b  \\
         \% (95\% CI)
    \end{tabular}\\
    \toprule

    \textbf{Overall}



    & \quad  & \quad  & \quad  & \quad  \\

    \quad Male  & $\circ(\circ)$ & $\circ(\circ)$  & $\circ(\circ)$ & $\circ(\circ)$ \\
    \quad Female  & $\circ(\circ)$ & $\circ(\circ)$  & $\circ(\circ)$ & $\circ(\circ)$ \\
    \textbf{Race/ethnicity} & $\circ(\circ)$ & $\circ(\circ)$  & $\circ(\circ)$ & $\circ(\circ)$ \\
   \quad White, non-hispanic & $\circ(\circ)$ & $\circ(\circ)$  & $\circ(\circ)$ & $\circ(\circ)$ \\
    \quad \quad Male & $\circ(\circ)$ & $\circ(\circ)$  & $\circ(\circ)$ & $\circ(\circ)$ \\
    \quad \quad Female & $\circ(\circ)$ & $\circ(\circ)$  & $\circ(\circ)$ & $\circ(\circ)$ \\

     \Xhline{2\arrayrulewidth}
\end{tabular}

\end{document}