Question 110
Find all functions $f: \mathbb{Z}^+ \rightarrow \mathbb{Z}^+$ satisfying the following conditions:
* For all $x, y \in \mathbb{Z}^+$, $f(x) + f(y)$ is divisible by $x + y$.
* For any integer $x \ge 1395$, the inequality $2f(x) \le x^3$ holds.
* For all $x, y \in \mathbb{Z}^+$, $f(x) + f(y)$ is divisible by $x + y$.
* For any integer $x \ge 1395$, the inequality $2f(x) \le x^3$ holds.