Calcule la suma de cifras de N.
\[\begin{array}{|c|c|c|}\hline & 4 & \\ \hline2 & 4 & 6 \\ \hline &5 & \\\hline\end{array}\] \[\begin{array}{|c|c|c|}\hline & 2 & \\ \hline9 & 8 & 13 \\ \hline & 4 & \\\hline\end{array}\] \[\begin{array}{|c|c|c|}\hline & 15 & \\ \hline5 & 15 & 8 \\ \hline & 20 & \\\hline\end{array}\] \[\begin{array}{|c|c|c|}\hline & 9 & \\ \hline0 & N & 4 \\ \hline & 16 & \\\hline\end{array}\]