\[\begin{array}{l} {\text{Simplify}}: \hfill \\ \sqrt {\sqrt 6 + \sqrt 2 + 1} + \sqrt {\sqrt 6 + \sqrt 2 - 1} + \sqrt {\sqrt 6 - \sqrt 2 + 1} + \sqrt {\sqrt 6 - \sqrt 2 - 1} . \hfill \\ \end{array} \]