# Define a compact and convex set through inequality constraints

I need to find twice continuously differentiable functions $g_i: \mathbb{R}^2 \rightarrow \mathbb{R}$ $i=1,...,I$ such that the set $\{ 0,1\}^2=\{(0,0), (1,0), (0,1), (1,1) \}$ can be written as $\{x \in \mathbb{R}^2 \text{ s.t. } g_i(x)\leq 0 \text{ } \forall i=1,...,I \}$. Could you help me?

Hint: Try to construct a function $g$ which is $\geq0$ everywhere and has roots in $\{0,1\}^2.$
For this, first try to construct a function $h$ which is $\geq 0$ and has a root in $(0,0)$. Then, do the same for the other values in $\{0,1\}^2$. The function you are looking for is the product of the four functions you get that way.