## Ending a vertical line

I have the following code
\begin{flushleft}
\begin{tabular}{ |c|c|c c| }
\hline
0 & 2 & 8 & 10 \\
1 & 3 & 9 & 11 \\
\cline{1-2}
4 & 6 & 12 & 14 \\
5 & 7 & 13 & 15 \\
\hline
16 & 18 & 24 & 26 \\
17 & 19 & 25 & 27 \\
20 & 22 & 28 & 30 \\
21 & 23 & 29 & 31 \\
\hline
\end{tabular}
\tab has $2^5$ elements
\end{flushleft}
The vertical lines extend the entire length of the table but I only need the vertical lines to extend halfway down the table. How can I do this?