Question 92
A graph $G$ with $n$ vertices is called *great* if we can label each vertex with a different positive integer not exceeding $\left\lfloor \frac{n^2}{4} \right\rfloor$ and find a set of non-negative integers $D$ so that there is an edge between two vertices if and only if the difference between their labels is in $D$. Show that if $n$ is sufficiently large we can always find a graph with $n$ vertices which is not great.