# Behavior of Poisson Integral Formula for Half Space

I am trying to solve the following:

If $$g$$ is bounded and $$g(x)=|x|$$ for $$x\in \mathbb{R}^{n-1}$$ such that $$|x|\leq 1$$, then $$Du$$ is unbounded in a neighboorhood of zero.

Remembering that: the problem is $$\left\{\begin{array}{ll} \Delta u = 0 , \ in \ \mathbb{R}_{+}^{n} \\ u=g , \ in \ \mathbb{R}^{n-1} \end{array}\right.$$ and $$u(x)=\int\limits_{\mathbb{R}^{n-1}}\dfrac{2x_{n}}{n\omega_{n}|x-y|^{n}}g(y)dS_{y}$$.

I would be gratefull if some can give me some help.