Problem 4.
The former secret agent is now a contractor. His company works in
the Euclidean space $\mathbb{R}^3$. He has got a tool called the Gram-Schmidt
orthogonalization and a basis \{(-1, 0, 1), (1, 1, 3), (1, 3, -1)\} of $\mathbb{R}^3$.
Help him to construct an orthonormal basis of $\mathbb{R}^3$ out of the given
basis!