If $\bar{\mathrm{a}}$, $\bar{\mathrm{b}}$, $\bar{\mathrm{c}}$ are three vectors which are perpendicular to $\bar{\mathrm{b}} + \bar{\mathrm{c}}$, $\bar{\mathrm{c}} + \bar{\mathrm{a}}$ and $\bar{\mathrm{a}} + \bar{\mathrm{b}}$ respectively, such that $|\bar{a}| = 2$, $|\bar{b}| = 3$, $|\bar{c}| = 4$, then $|\bar{a} + \bar{b} + \bar{c}| =$