How can I prove this?
Given a simple graph $G=\langle V, E\rangle$ where $V$ is a set of vertices, $|V|=n$, and $E$ is a 2-element subset of $V$ with the edges of the graph. Also $\forall x,y\in V(G)$ if $\langle x,y\rangle\notin E(G)\Rightarrow\deg(x)+\deg(y)\ge n-1$. Prove there exists a simple path $p$ with length $n$.