Here $G_{n}$ denotes a simple undirected graph with $n$ vertices, $K_{n}$ denotes the complete graph with $n$ vertices, $K_{n,m}$ the complete bipartite graph whose components have $m$ and $n$ vertices, and $C_{n}$ a circuit with $n$ vertices. The number of edges in the graph $G_{n}$ is denoted $e(G_{n})$. If $e(G_{n}) \geq\frac{n\sqrt{n}}{2}+\frac{n}{4}$ ,prove that $G_{n}$ contains $C_{4}$ .
Problem
Source: 12-th Hungary-Israel Mathematical Competition 2001
Tags: graph theory, combinatorics proposed, combinatorics