If the vectors $\bar{p}, \bar{q}$ and $\bar{r}$ are such that $(\bar{q} \times \bar{r}) \times(\bar{r} \times \bar{p})=3 \bar{r}$ then $[\bar{p} \times \bar{q} \bar{q} \times \bar{r} \bar{r} \times \bar{p}]=$