Orthogonality & Least Squares · Easy problem

Let $W$ be the subspace of $\mathbb R^5$ spanned by $(1, 0, 1, 0, 1)$, $(0, 1, 0, 1, 0)$ and $(1, 1, 1, 1, 1)$. Find the dimension of the orthogonal complement $W^{\perp}$.