In an octagon ABCDEFGH of equal side, what is the sum of
$\overrightarrow{\mathrm{AB}}+\overrightarrow{\mathrm{AC}}+\overrightarrow{\mathrm{AD}}+\overrightarrow{\mathrm{AE}}+\overrightarrow{\mathrm{AF}}+\overrightarrow{\mathrm{AG}}+\overrightarrow{\mathrm{AH}}$
if, $\overrightarrow{A O}=2 \hat{i}+3 \hat{j}-4 \hat{k}$