If $\overrightarrow a,\overrightarrow b,\overrightarrow c$ are non zero, non collinear vectors such that $\overrightarrow a\times\overrightarrow b=\overrightarrow b\times\overrightarrow c=\overrightarrow c\times\overrightarrow a$, then $\overrightarrow a+\overrightarrow b+\overrightarrow c=?$

Question

$\begin{array}{1 1} 3\overrightarrow a \\ \overrightarrow 0 \\ unit \;vector \\ \overrightarrow a \end{array} $